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<title>Welcome to Flask — Flask Documentation (3.2.x)</title>
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<title>Application Structure and Lifecycle — Flask Documentation (3.2.x)</title>
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<section class="hide-header" id="welcome-to-flask">
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<h1>Welcome to Flask<a class="headerlink" href="#welcome-to-flask" title="Link to this heading">¶</a></h1>
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<img alt="_images/flask-horizontal.png" class="align-center" src="_images/flask-horizontal.png" />
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<p>Welcome to Flask’s documentation. Flask is a lightweight WSGI web application framework.
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It is designed to make getting started quick and easy, with the ability to scale up to
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complex applications.</p>
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<p>Get started with <a class="reference internal" href="installation.html"><span class="doc">Installation</span></a>
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more detailed <a class="reference internal" href="tutorial/index.html"><span class="doc">Tutorial</span></a> that shows how to create a small but
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complete application with Flask. Common patterns are described in the
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<a class="reference internal" href="patterns/index.html"><span class="doc">Patterns for Flask</span></a> section. The rest of the docs describe each
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component of Flask in detail, with a full reference in the <a class="reference internal" href="api.html"><span class="doc">API</span></a>
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section.</p>
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<p>Flask depends on the <a class="reference external" href="https://werkzeug.palletsprojects.com">Werkzeug</a> WSGI toolkit, the <a class="reference external" href="https://jinja.palletsprojects.com">Jinja</a> template engine, and the
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<a class="reference external" href="https://click.palletsprojects.com">Click</a> CLI toolkit. Be sure to check their documentation as well as Flask’s when
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looking for information.</p>
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<section id="user-s-guide">
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<h2>User’s Guide<a class="headerlink" href="#user-s-guide" title="Link to this heading">¶</a></h2>
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<p>Flask provides configuration and conventions, with sensible defaults, to get started.
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This section of the documentation explains the different parts of the Flask framework
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and how they can be used, customized, and extended. Beyond Flask itself, look for
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community-maintained extensions to add even more functionality.</p>
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<li class="toctree-l2"><a class="reference internal" href="quickstart.html#a-minimal-application">A Minimal Application</a></li>
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<li class="toctree-l2"><a class="reference internal" href="quickstart.html#debug-mode">Debug Mode</a></li>
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<li class="toctree-l2"><a class="reference internal" href="quickstart.html#accessing-request-data">Accessing Request Data</a></li>
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<li class="toctree-l2"><a class="reference internal" href="quickstart.html#redirects-and-errors">Redirects and Errors</a></li>
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<li class="toctree-l2"><a class="reference internal" href="quickstart.html#using-flask-extensions">Using Flask Extensions</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/factory.html">Application Setup</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/database.html">Define and Access the Database</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/views.html">Blueprints and Views</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/templates.html">Templates</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/static.html">Static Files</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/blog.html">Blog Blueprint</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/install.html">Make the Project Installable</a></li>
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<li class="toctree-l2"><a class="reference internal" href="tutorial/next.html">Keep Developing!</a></li>
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<li class="toctree-l1"><a class="reference internal" href="templating.html">Templates</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="templating.html#jinja-setup">Jinja Setup</a></li>
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<li class="toctree-l2"><a class="reference internal" href="templating.html#standard-context">Standard Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="templating.html#controlling-autoescaping">Controlling Autoescaping</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="testing.html">Testing Flask Applications</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="testing.html#identifying-tests">Identifying Tests</a></li>
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<li class="toctree-l2"><a class="reference internal" href="testing.html#sending-requests-with-the-test-client">Sending Requests with the Test Client</a></li>
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<li class="toctree-l2"><a class="reference internal" href="testing.html#following-redirects">Following Redirects</a></li>
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<li class="toctree-l2"><a class="reference internal" href="testing.html#accessing-and-modifying-the-session">Accessing and Modifying the Session</a></li>
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<li class="toctree-l2"><a class="reference internal" href="testing.html#running-commands-with-the-cli-runner">Running Commands with the CLI Runner</a></li>
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<li class="toctree-l2"><a class="reference internal" href="testing.html#tests-that-depend-on-an-active-context">Tests that depend on an Active Context</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="errorhandling.html">Handling Application Errors</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#error-logging-tools">Error Logging Tools</a></li>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#error-handlers">Error Handlers</a></li>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#custom-error-pages">Custom Error Pages</a></li>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#blueprint-error-handlers">Blueprint Error Handlers</a></li>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#returning-api-errors-as-json">Returning API Errors as JSON</a></li>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#logging">Logging</a></li>
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<li class="toctree-l2"><a class="reference internal" href="errorhandling.html#debugging">Debugging</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="debugging.html">Debugging Application Errors</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="debugging.html#in-production">In Production</a></li>
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<li class="toctree-l2"><a class="reference internal" href="debugging.html#the-built-in-debugger">The Built-In Debugger</a></li>
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<li class="toctree-l2"><a class="reference internal" href="debugging.html#external-debuggers">External Debuggers</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="logging.html">Logging</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="logging.html#basic-configuration">Basic Configuration</a></li>
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<li class="toctree-l2"><a class="reference internal" href="logging.html#email-errors-to-admins">Email Errors to Admins</a></li>
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<li class="toctree-l2"><a class="reference internal" href="logging.html#injecting-request-information">Injecting Request Information</a></li>
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<li class="toctree-l2"><a class="reference internal" href="logging.html#other-libraries">Other Libraries</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="config.html">Configuration Handling</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="config.html#configuration-basics">Configuration Basics</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#debug-mode">Debug Mode</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#builtin-configuration-values">Builtin Configuration Values</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#configuring-from-python-files">Configuring from Python Files</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#configuring-from-data-files">Configuring from Data Files</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#configuration-best-practices">Configuration Best Practices</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#development-production">Development / Production</a></li>
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<li class="toctree-l2"><a class="reference internal" href="config.html#instance-folders">Instance Folders</a></li>
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</ul>
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<li class="toctree-l1"><a class="reference internal" href="signals.html">Signals</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="signals.html#core-signals">Core Signals</a></li>
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<li class="toctree-l2"><a class="reference internal" href="signals.html#subscribing-to-signals">Subscribing to Signals</a></li>
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<li class="toctree-l2"><a class="reference internal" href="signals.html#creating-signals">Creating Signals</a></li>
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<li class="toctree-l2"><a class="reference internal" href="signals.html#sending-signals">Sending Signals</a></li>
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<li class="toctree-l2"><a class="reference internal" href="signals.html#signals-and-flask-s-request-context">Signals and Flask’s Request Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="signals.html#decorator-based-signal-subscriptions">Decorator Based Signal Subscriptions</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="views.html">Class-based Views</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="views.html#basic-reusable-view">Basic Reusable View</a></li>
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<li class="toctree-l2"><a class="reference internal" href="views.html#url-variables">URL Variables</a></li>
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<li class="toctree-l2"><a class="reference internal" href="views.html#view-lifetime-and-self">View Lifetime and <code class="docutils literal notranslate"><span class="pre">self</span></code></a></li>
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<li class="toctree-l2"><a class="reference internal" href="views.html#view-decorators">View Decorators</a></li>
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<li class="toctree-l2"><a class="reference internal" href="views.html#method-dispatching-and-apis">Method Dispatching and APIs</a></li>
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<li class="toctree-l1"><a class="reference internal" href="lifecycle.html">Application Structure and Lifecycle</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="lifecycle.html#application-setup">Application Setup</a></li>
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<li class="toctree-l2"><a class="reference internal" href="lifecycle.html#serving-the-application">Serving the Application</a></li>
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<li class="toctree-l2"><a class="reference internal" href="lifecycle.html#how-a-request-is-handled">How a Request is Handled</a></li>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="appcontext.html">The Application Context</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="appcontext.html#purpose-of-the-context">Purpose of the Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="appcontext.html#lifetime-of-the-context">Lifetime of the Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="appcontext.html#manually-push-a-context">Manually Push a Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="appcontext.html#storing-data">Storing Data</a></li>
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<li class="toctree-l2"><a class="reference internal" href="appcontext.html#events-and-signals">Events and Signals</a></li>
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</ul>
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</li>
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<li class="toctree-l1"><a class="reference internal" href="reqcontext.html">The Request Context</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="reqcontext.html#purpose-of-the-context">Purpose of the Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="reqcontext.html#lifetime-of-the-context">Lifetime of the Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="reqcontext.html#manually-push-a-context">Manually Push a Context</a></li>
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<li class="toctree-l2"><a class="reference internal" href="reqcontext.html#how-the-context-works">How the Context Works</a></li>
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<li class="toctree-l2"><a class="reference internal" href="reqcontext.html#callbacks-and-errors">Callbacks and Errors</a></li>
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<li class="toctree-l2"><a class="reference internal" href="reqcontext.html#notes-on-proxies">Notes On Proxies</a></li>
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<li class="toctree-l1"><a class="reference internal" href="blueprints.html">Modular Applications with Blueprints</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#why-blueprints">Why Blueprints?</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#the-concept-of-blueprints">The Concept of Blueprints</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#my-first-blueprint">My First Blueprint</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#registering-blueprints">Registering Blueprints</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#nesting-blueprints">Nesting Blueprints</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#blueprint-resources">Blueprint Resources</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#building-urls">Building URLs</a></li>
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<li class="toctree-l2"><a class="reference internal" href="blueprints.html#blueprint-error-handlers">Blueprint Error Handlers</a></li>
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<li class="toctree-l1"><a class="reference internal" href="extensions.html">Extensions</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="extensions.html#using-extensions">Using Extensions</a></li>
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<li class="toctree-l2"><a class="reference internal" href="extensions.html#building-extensions">Building Extensions</a></li>
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<li class="toctree-l1"><a class="reference internal" href="cli.html">Command Line Interface</a><ul>
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<li class="toctree-l2"><a class="reference internal" href="cli.html#environment-variables-from-virtualenv">Environment Variables From virtualenv</a></li>
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<li class="toctree-l2"><a class="reference internal" href="cli.html#custom-commands">Custom Commands</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="cli.html#plugins">Plugins</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="cli.html#custom-scripts">Custom Scripts</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="cli.html#pycharm-integration">PyCharm Integration</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="server.html">Development Server</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="server.html#command-line">Command Line</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="server.html#in-code">In Code</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="shell.html">Working with the Shell</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="shell.html#command-line-interface">Command Line Interface</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="shell.html#creating-a-request-context">Creating a Request Context</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="shell.html#firing-before-after-request">Firing Before/After Request</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="shell.html#further-improving-the-shell-experience">Further Improving the Shell Experience</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="patterns/index.html">Patterns for Flask</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/packages.html">Large Applications as Packages</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/appfactories.html">Application Factories</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/appdispatch.html">Application Dispatching</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/urlprocessors.html">Using URL Processors</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/sqlite3.html">Using SQLite 3 with Flask</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/sqlalchemy.html">SQLAlchemy in Flask</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/fileuploads.html">Uploading Files</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/caching.html">Caching</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/viewdecorators.html">View Decorators</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/wtforms.html">Form Validation with WTForms</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/templateinheritance.html">Template Inheritance</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/flashing.html">Message Flashing</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/javascript.html">JavaScript, <code class="docutils literal notranslate"><span class="pre">fetch</span></code>, and JSON</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/lazyloading.html">Lazily Loading Views</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/mongoengine.html">MongoDB with MongoEngine</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/favicon.html">Adding a favicon</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/streaming.html">Streaming Contents</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/deferredcallbacks.html">Deferred Request Callbacks</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/methodoverrides.html">Adding HTTP Method Overrides</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/requestchecksum.html">Request Content Checksums</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/celery.html">Background Tasks with Celery</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/subclassing.html">Subclassing Flask</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="patterns/singlepageapplications.html">Single-Page Applications</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="web-security.html">Security Considerations</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="web-security.html#resource-use">Resource Use</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="web-security.html#cross-site-scripting-xss">Cross-Site Scripting (XSS)</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="web-security.html#cross-site-request-forgery-csrf">Cross-Site Request Forgery (CSRF)</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="web-security.html#json-security">JSON Security</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="web-security.html#security-headers">Security Headers</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="web-security.html#copy-paste-to-terminal">Copy/Paste to Terminal</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="deploying/index.html">Deploying to Production</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="deploying/index.html#self-hosted-options">Self-Hosted Options</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="deploying/index.html#hosting-platforms">Hosting Platforms</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="async-await.html">Using <code class="docutils literal notranslate"><span class="pre">async</span></code> and <code class="docutils literal notranslate"><span class="pre">await</span></code></a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="async-await.html#performance">Performance</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="async-await.html#background-tasks">Background tasks</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="async-await.html#when-to-use-quart-instead">When to use Quart instead</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="async-await.html#extensions">Extensions</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="async-await.html#other-event-loops">Other event loops</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
</ul>
|
||||
|
||||
<section id="application-structure-and-lifecycle">
|
||||
<h1>Application Structure and Lifecycle<a class="headerlink" href="#application-structure-and-lifecycle" title="Link to this heading">¶</a></h1>
|
||||
<p>Flask makes it pretty easy to write a web application. But there are quite a few
|
||||
different parts to an application and to each request it handles. Knowing what happens
|
||||
during application setup, serving, and handling requests will help you know what’s
|
||||
possible in Flask and how to structure your application.</p>
|
||||
<section id="application-setup">
|
||||
<h2>Application Setup<a class="headerlink" href="#application-setup" title="Link to this heading">¶</a></h2>
|
||||
<p>The first step in creating a Flask application is creating the application object. Each
|
||||
Flask application is an instance of the <a class="reference internal" href="api.html#flask.Flask" title="flask.Flask"><code class="xref py py-class docutils literal notranslate"><span class="pre">Flask</span></code></a> class, which collects all
|
||||
configuration, extensions, and views.</p>
|
||||
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">flask</span><span class="w"> </span><span class="kn">import</span> <span class="n">Flask</span>
|
||||
|
||||
<span class="n">app</span> <span class="o">=</span> <span class="n">Flask</span><span class="p">(</span><span class="vm">__name__</span><span class="p">)</span>
|
||||
<span class="n">app</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">from_mapping</span><span class="p">(</span>
|
||||
<span class="n">SECRET_KEY</span><span class="o">=</span><span class="s2">"dev"</span><span class="p">,</span>
|
||||
<span class="p">)</span>
|
||||
<span class="n">app</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">from_prefixed_env</span><span class="p">()</span>
|
||||
|
||||
<span class="nd">@app</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s2">"/"</span><span class="p">)</span>
|
||||
<span class="k">def</span><span class="w"> </span><span class="nf">index</span><span class="p">():</span>
|
||||
<span class="k">return</span> <span class="s2">"Hello, World!"</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>This is known as the “application setup phase”, it’s the code you write that’s outside
|
||||
any view functions or other handlers. It can be split up between different modules and
|
||||
sub-packages, but all code that you want to be part of your application must be imported
|
||||
in order for it to be registered.</p>
|
||||
<p>All application setup must be completed before you start serving your application and
|
||||
handling requests. This is because WSGI servers divide work between multiple workers, or
|
||||
can be distributed across multiple machines. If the configuration changed in one worker,
|
||||
there’s no way for Flask to ensure consistency between other workers.</p>
|
||||
<p>Flask tries to help developers catch some of these setup ordering issues by showing an
|
||||
error if setup-related methods are called after requests are handled. In that case
|
||||
you’ll see this error:</p>
|
||||
<blockquote>
|
||||
<div><p>The setup method ‘route’ can no longer be called on the application. It has already
|
||||
handled its first request, any changes will not be applied consistently.
|
||||
Make sure all imports, decorators, functions, etc. needed to set up the application
|
||||
are done before running it.</p>
|
||||
</div></blockquote>
|
||||
<p>However, it is not possible for Flask to detect all cases of out-of-order setup. In
|
||||
general, don’t do anything to modify the <code class="docutils literal notranslate"><span class="pre">Flask</span></code> app object and <code class="docutils literal notranslate"><span class="pre">Blueprint</span></code> objects
|
||||
from within view functions that run during requests. This includes:</p>
|
||||
<ul class="simple">
|
||||
<li><p>Adding routes, view functions, and other request handlers with <code class="docutils literal notranslate"><span class="pre">@app.route</span></code>,
|
||||
<code class="docutils literal notranslate"><span class="pre">@app.errorhandler</span></code>, <code class="docutils literal notranslate"><span class="pre">@app.before_request</span></code>, etc.</p></li>
|
||||
<li><p>Registering blueprints.</p></li>
|
||||
<li><p>Loading configuration with <code class="docutils literal notranslate"><span class="pre">app.config</span></code>.</p></li>
|
||||
<li><p>Setting up the Jinja template environment with <code class="docutils literal notranslate"><span class="pre">app.jinja_env</span></code>.</p></li>
|
||||
<li><p>Setting a session interface, instead of the default itsdangerous cookie.</p></li>
|
||||
<li><p>Setting a JSON provider with <code class="docutils literal notranslate"><span class="pre">app.json</span></code>, instead of the default provider.</p></li>
|
||||
<li><p>Creating and initializing Flask extensions.</p></li>
|
||||
</ul>
|
||||
</section>
|
||||
<section id="api-reference">
|
||||
<h2>API Reference<a class="headerlink" href="#api-reference" title="Link to this heading">¶</a></h2>
|
||||
<p>If you are looking for information on a specific function, class or
|
||||
method, this part of the documentation is for you.</p>
|
||||
<div class="toctree-wrapper compound">
|
||||
<ul>
|
||||
<li class="toctree-l1"><a class="reference internal" href="api.html">API</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#application-object">Application Object</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#blueprint-objects">Blueprint Objects</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#incoming-request-data">Incoming Request Data</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#response-objects">Response Objects</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#sessions">Sessions</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#session-interface">Session Interface</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#test-client">Test Client</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#test-cli-runner">Test CLI Runner</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#application-globals">Application Globals</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#useful-functions-and-classes">Useful Functions and Classes</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#message-flashing">Message Flashing</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#module-flask.json">JSON Support</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#template-rendering">Template Rendering</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#configuration">Configuration</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#stream-helpers">Stream Helpers</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#useful-internals">Useful Internals</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#signals">Signals</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#class-based-views">Class-Based Views</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#url-route-registrations">URL Route Registrations</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#view-function-options">View Function Options</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="api.html#command-line-interface">Command Line Interface</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
</ul>
|
||||
</div>
|
||||
<section id="serving-the-application">
|
||||
<h2>Serving the Application<a class="headerlink" href="#serving-the-application" title="Link to this heading">¶</a></h2>
|
||||
<p>Flask is a WSGI application framework. The other half of WSGI is the WSGI server. During
|
||||
development, Flask, through Werkzeug, provides a development WSGI server with the
|
||||
<code class="docutils literal notranslate"><span class="pre">flask</span> <span class="pre">run</span></code> CLI command. When you are done with development, use a production server
|
||||
to serve your application, see <a class="reference internal" href="deploying/index.html"><span class="doc">Deploying to Production</span></a>.</p>
|
||||
<p>Regardless of what server you’re using, it will follow the <span class="target" id="index-0"></span><a class="pep reference external" href="https://peps.python.org/pep-3333/"><strong>PEP 3333</strong></a> WSGI spec. The
|
||||
WSGI server will be told how to access your Flask application object, which is the WSGI
|
||||
application. Then it will start listening for HTTP requests, translate the request data
|
||||
into a WSGI environ, and call the WSGI application with that data. The WSGI application
|
||||
will return data that is translated into an HTTP response.</p>
|
||||
<ol class="arabic simple">
|
||||
<li><p>Browser or other client makes HTTP request.</p></li>
|
||||
<li><p>WSGI server receives request.</p></li>
|
||||
<li><p>WSGI server converts HTTP data to WSGI <code class="docutils literal notranslate"><span class="pre">environ</span></code> dict.</p></li>
|
||||
<li><p>WSGI server calls WSGI application with the <code class="docutils literal notranslate"><span class="pre">environ</span></code>.</p></li>
|
||||
<li><p>Flask, the WSGI application, does all its internal processing to route the request
|
||||
to a view function, handle errors, etc.</p></li>
|
||||
<li><p>Flask translates View function return into WSGI response data, passes it to WSGI
|
||||
server.</p></li>
|
||||
<li><p>WSGI server creates and send an HTTP response.</p></li>
|
||||
<li><p>Client receives the HTTP response.</p></li>
|
||||
</ol>
|
||||
<section id="middleware">
|
||||
<h3>Middleware<a class="headerlink" href="#middleware" title="Link to this heading">¶</a></h3>
|
||||
<p>The WSGI application above is a callable that behaves in a certain way. Middleware
|
||||
is a WSGI application that wraps another WSGI application. It’s a similar concept to
|
||||
Python decorators. The outermost middleware will be called by the server. It can modify
|
||||
the data passed to it, then call the WSGI application (or further middleware) that it
|
||||
wraps, and so on. And it can take the return value of that call and modify it further.</p>
|
||||
<p>From the WSGI server’s perspective, there is one WSGI application, the one it calls
|
||||
directly. Typically, Flask is the “real” application at the end of the chain of
|
||||
middleware. But even Flask can call further WSGI applications, although that’s an
|
||||
advanced, uncommon use case.</p>
|
||||
<p>A common middleware you’ll see used with Flask is Werkzeug’s
|
||||
<a class="reference external" href="https://werkzeug.palletsprojects.com/en/stable/middleware/proxy_fix/#werkzeug.middleware.proxy_fix.ProxyFix" title="(in Werkzeug v3.1.x)"><code class="xref py py-class docutils literal notranslate"><span class="pre">ProxyFix</span></code></a>, which modifies the request to look
|
||||
like it came directly from a client even if it passed through HTTP proxies on the way.
|
||||
There are other middleware that can handle serving static files, authentication, etc.</p>
|
||||
</section>
|
||||
<section id="additional-notes">
|
||||
<h2>Additional Notes<a class="headerlink" href="#additional-notes" title="Link to this heading">¶</a></h2>
|
||||
<div class="toctree-wrapper compound">
|
||||
<ul>
|
||||
<li class="toctree-l1"><a class="reference internal" href="design.html">Design Decisions in Flask</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#the-explicit-application-object">The Explicit Application Object</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#the-routing-system">The Routing System</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#one-template-engine">One Template Engine</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#what-does-micro-mean">What does “micro” mean?</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#thread-locals">Thread Locals</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#async-await-and-asgi-support">Async/await and ASGI support</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="design.html#what-flask-is-what-flask-is-not">What Flask is, What Flask is Not</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="extensiondev.html">Flask Extension Development</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#naming">Naming</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#the-extension-class-and-initialization">The Extension Class and Initialization</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#adding-behavior">Adding Behavior</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#configuration-techniques">Configuration Techniques</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#data-during-a-request">Data During a Request</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#views-and-models">Views and Models</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="extensiondev.html#recommended-extension-guidelines">Recommended Extension Guidelines</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="contributing.html">Contributing</a></li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="license.html">BSD-3-Clause License</a></li>
|
||||
<li class="toctree-l1"><a class="reference internal" href="changes.html">Changes</a><ul>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-2-0">Version 3.2.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-1-1">Version 3.1.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-1-0">Version 3.1.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-0-3">Version 3.0.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-0-2">Version 3.0.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-0-1">Version 3.0.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-3-0-0">Version 3.0.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-3-3">Version 2.3.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-3-2">Version 2.3.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-3-1">Version 2.3.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-3-0">Version 2.3.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-2-5">Version 2.2.5</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-2-4">Version 2.2.4</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-2-3">Version 2.2.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-2-2">Version 2.2.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-2-1">Version 2.2.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-2-0">Version 2.2.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-1-3">Version 2.1.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-1-2">Version 2.1.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-1-1">Version 2.1.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-1-0">Version 2.1.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-0-3">Version 2.0.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-0-2">Version 2.0.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-0-1">Version 2.0.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-2-0-0">Version 2.0.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-1-4">Version 1.1.4</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-1-3">Version 1.1.3</a></li>
|
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<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-1-2">Version 1.1.2</a></li>
|
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<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-1-1">Version 1.1.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-1-0">Version 1.1.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-0-4">Version 1.0.4</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-0-3">Version 1.0.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-0-2">Version 1.0.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-0-1">Version 1.0.1</a></li>
|
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<li class="toctree-l2"><a class="reference internal" href="changes.html#version-1-0">Version 1.0</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-12-5">Version 0.12.5</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-12-4">Version 0.12.4</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-12-3">Version 0.12.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-12-2">Version 0.12.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-12-1">Version 0.12.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-12">Version 0.12</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-11-1">Version 0.11.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-11">Version 0.11</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-10-1">Version 0.10.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-10">Version 0.10</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-9">Version 0.9</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-8-1">Version 0.8.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-8">Version 0.8</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-7-2">Version 0.7.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-7-1">Version 0.7.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-7">Version 0.7</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-6-1">Version 0.6.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-6">Version 0.6</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-5-2">Version 0.5.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-5-1">Version 0.5.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-5">Version 0.5</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-4">Version 0.4</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-3-1">Version 0.3.1</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-3">Version 0.3</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-2">Version 0.2</a></li>
|
||||
<li class="toctree-l2"><a class="reference internal" href="changes.html#version-0-1">Version 0.1</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
</ul>
|
||||
</div>
|
||||
</section>
|
||||
<section id="how-a-request-is-handled">
|
||||
<h2>How a Request is Handled<a class="headerlink" href="#how-a-request-is-handled" title="Link to this heading">¶</a></h2>
|
||||
<p>For us, the interesting part of the steps above is when Flask gets called by the WSGI
|
||||
server (or middleware). At that point, it will do quite a lot to handle the request and
|
||||
generate the response. At the most basic, it will match the URL to a view function, call
|
||||
the view function, and pass the return value back to the server. But there are many more
|
||||
parts that you can use to customize its behavior.</p>
|
||||
<ol class="arabic simple">
|
||||
<li><p>WSGI server calls the Flask object, which calls <a class="reference internal" href="api.html#flask.Flask.wsgi_app" title="flask.Flask.wsgi_app"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Flask.wsgi_app()</span></code></a>.</p></li>
|
||||
<li><p>A <a class="reference internal" href="api.html#flask.ctx.RequestContext" title="flask.ctx.RequestContext"><code class="xref py py-class docutils literal notranslate"><span class="pre">RequestContext</span></code></a> object is created. This converts the WSGI <code class="docutils literal notranslate"><span class="pre">environ</span></code>
|
||||
dict into a <a class="reference internal" href="api.html#flask.Request" title="flask.Request"><code class="xref py py-class docutils literal notranslate"><span class="pre">Request</span></code></a> object. It also creates an <code class="xref py py-class docutils literal notranslate"><span class="pre">AppContext</span></code> object.</p></li>
|
||||
<li><p>The <a class="reference internal" href="appcontext.html"><span class="doc">app context</span></a> is pushed, which makes <a class="reference internal" href="api.html#flask.current_app" title="flask.current_app"><code class="xref py py-data docutils literal notranslate"><span class="pre">current_app</span></code></a> and
|
||||
<a class="reference internal" href="api.html#flask.g" title="flask.g"><code class="xref py py-data docutils literal notranslate"><span class="pre">g</span></code></a> available.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.appcontext_pushed" title="flask.appcontext_pushed"><code class="xref py py-data docutils literal notranslate"><span class="pre">appcontext_pushed</span></code></a> signal is sent.</p></li>
|
||||
<li><p>The <a class="reference internal" href="reqcontext.html"><span class="doc">request context</span></a> is pushed, which makes <a class="reference internal" href="api.html#flask.request" title="flask.request"><code class="xref py py-attr docutils literal notranslate"><span class="pre">request</span></code></a> and
|
||||
<a class="reference internal" href="api.html#flask.session" title="flask.session"><code class="xref py py-class docutils literal notranslate"><span class="pre">session</span></code></a> available.</p></li>
|
||||
<li><p>The session is opened, loading any existing session data using the app’s
|
||||
<a class="reference internal" href="api.html#flask.Flask.session_interface" title="flask.Flask.session_interface"><code class="xref py py-attr docutils literal notranslate"><span class="pre">session_interface</span></code></a>, an instance of <a class="reference internal" href="api.html#flask.sessions.SessionInterface" title="flask.sessions.SessionInterface"><code class="xref py py-class docutils literal notranslate"><span class="pre">SessionInterface</span></code></a>.</p></li>
|
||||
<li><p>The URL is matched against the URL rules registered with the <a class="reference internal" href="api.html#flask.Flask.route" title="flask.Flask.route"><code class="xref py py-meth docutils literal notranslate"><span class="pre">route()</span></code></a>
|
||||
decorator during application setup. If there is no match, the error - usually a 404,
|
||||
405, or redirect - is stored to be handled later.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.request_started" title="flask.request_started"><code class="xref py py-data docutils literal notranslate"><span class="pre">request_started</span></code></a> signal is sent.</p></li>
|
||||
<li><p>Any <a class="reference internal" href="api.html#flask.Flask.url_value_preprocessor" title="flask.Flask.url_value_preprocessor"><code class="xref py py-meth docutils literal notranslate"><span class="pre">url_value_preprocessor()</span></code></a> decorated functions are called.</p></li>
|
||||
<li><p>Any <a class="reference internal" href="api.html#flask.Flask.before_request" title="flask.Flask.before_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">before_request()</span></code></a> decorated functions are called. If any of
|
||||
these function returns a value it is treated as the response immediately.</p></li>
|
||||
<li><p>If the URL didn’t match a route a few steps ago, that error is raised now.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.Flask.route" title="flask.Flask.route"><code class="xref py py-meth docutils literal notranslate"><span class="pre">route()</span></code></a> decorated view function associated with the matched URL
|
||||
is called and returns a value to be used as the response.</p></li>
|
||||
<li><p>If any step so far raised an exception, and there is an <a class="reference internal" href="api.html#flask.Flask.errorhandler" title="flask.Flask.errorhandler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">errorhandler()</span></code></a>
|
||||
decorated function that matches the exception class or HTTP error code, it is
|
||||
called to handle the error and return a response.</p></li>
|
||||
<li><p>Whatever returned a response value - a before request function, the view, or an
|
||||
error handler, that value is converted to a <a class="reference internal" href="api.html#flask.Response" title="flask.Response"><code class="xref py py-class docutils literal notranslate"><span class="pre">Response</span></code></a> object.</p></li>
|
||||
<li><p>Any <a class="reference internal" href="api.html#flask.after_this_request" title="flask.after_this_request"><code class="xref py py-func docutils literal notranslate"><span class="pre">after_this_request()</span></code></a> decorated functions are called, then cleared.</p></li>
|
||||
<li><p>Any <a class="reference internal" href="api.html#flask.Flask.after_request" title="flask.Flask.after_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">after_request()</span></code></a> decorated functions are called, which can modify
|
||||
the response object.</p></li>
|
||||
<li><p>The session is saved, persisting any modified session data using the app’s
|
||||
<a class="reference internal" href="api.html#flask.Flask.session_interface" title="flask.Flask.session_interface"><code class="xref py py-attr docutils literal notranslate"><span class="pre">session_interface</span></code></a>.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.request_finished" title="flask.request_finished"><code class="xref py py-data docutils literal notranslate"><span class="pre">request_finished</span></code></a> signal is sent.</p></li>
|
||||
<li><p>If any step so far raised an exception, and it was not handled by an error handler
|
||||
function, it is handled now. HTTP exceptions are treated as responses with their
|
||||
corresponding status code, other exceptions are converted to a generic 500 response.
|
||||
The <a class="reference internal" href="api.html#flask.got_request_exception" title="flask.got_request_exception"><code class="xref py py-data docutils literal notranslate"><span class="pre">got_request_exception</span></code></a> signal is sent.</p></li>
|
||||
<li><p>The response object’s status, headers, and body are returned to the WSGI server.</p></li>
|
||||
<li><p>Any <a class="reference internal" href="api.html#flask.Flask.teardown_request" title="flask.Flask.teardown_request"><code class="xref py py-meth docutils literal notranslate"><span class="pre">teardown_request()</span></code></a> decorated functions are called.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.request_tearing_down" title="flask.request_tearing_down"><code class="xref py py-data docutils literal notranslate"><span class="pre">request_tearing_down</span></code></a> signal is sent.</p></li>
|
||||
<li><p>The request context is popped, <a class="reference internal" href="api.html#flask.request" title="flask.request"><code class="xref py py-attr docutils literal notranslate"><span class="pre">request</span></code></a> and <a class="reference internal" href="api.html#flask.session" title="flask.session"><code class="xref py py-class docutils literal notranslate"><span class="pre">session</span></code></a> are no longer
|
||||
available.</p></li>
|
||||
<li><p>Any <a class="reference internal" href="api.html#flask.Flask.teardown_appcontext" title="flask.Flask.teardown_appcontext"><code class="xref py py-meth docutils literal notranslate"><span class="pre">teardown_appcontext()</span></code></a> decorated functions are called.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.appcontext_tearing_down" title="flask.appcontext_tearing_down"><code class="xref py py-data docutils literal notranslate"><span class="pre">appcontext_tearing_down</span></code></a> signal is sent.</p></li>
|
||||
<li><p>The app context is popped, <a class="reference internal" href="api.html#flask.current_app" title="flask.current_app"><code class="xref py py-data docutils literal notranslate"><span class="pre">current_app</span></code></a> and <a class="reference internal" href="api.html#flask.g" title="flask.g"><code class="xref py py-data docutils literal notranslate"><span class="pre">g</span></code></a> are no longer
|
||||
available.</p></li>
|
||||
<li><p>The <a class="reference internal" href="api.html#flask.appcontext_popped" title="flask.appcontext_popped"><code class="xref py py-data docutils literal notranslate"><span class="pre">appcontext_popped</span></code></a> signal is sent.</p></li>
|
||||
</ol>
|
||||
<p>There are even more decorators and customization points than this, but that aren’t part
|
||||
of every request lifecycle. They’re more specific to certain things you might use during
|
||||
a request, such as templates, building URLs, or handling JSON data. See the rest of this
|
||||
documentation, as well as the <a class="reference internal" href="api.html"><span class="doc">API</span></a> to explore further.</p>
|
||||
</section>
|
||||
</section>
|
||||
|
||||
|
|
@ -425,30 +207,34 @@ method, this part of the documentation is for you.</p>
|
|||
<span id="sidebar-top"></span>
|
||||
<div class="sphinxsidebar" role="navigation" aria-label="Main">
|
||||
<div class="sphinxsidebarwrapper">
|
||||
|
||||
|
||||
<h3>Project Links</h3>
|
||||
<ul>
|
||||
<li><a href="https://palletsprojects.com/donate">Donate</a>
|
||||
|
||||
<li><a href="https://pypi.org/project/Flask/">PyPI Releases</a>
|
||||
|
||||
<li><a href="https://github.com/pallets/flask/">Source Code</a>
|
||||
|
||||
<li><a href="https://github.com/pallets/flask/issues/">Issue Tracker</a>
|
||||
|
||||
<li><a href="https://discord.gg/pallets">Chat</a>
|
||||
</ul>
|
||||
|
||||
<p class="logo"><a href="index.html">
|
||||
<img class="logo" src="_static/flask-vertical.png" alt="Logo of Flask"/>
|
||||
</a></p>
|
||||
|
||||
|
||||
<h3>Contents</h3>
|
||||
<ul>
|
||||
<li><a class="reference internal" href="#">Welcome to Flask</a><ul>
|
||||
<li><a class="reference internal" href="#user-s-guide">User’s Guide</a></li>
|
||||
<li><a class="reference internal" href="#api-reference">API Reference</a></li>
|
||||
<li><a class="reference internal" href="#additional-notes">Additional Notes</a></li>
|
||||
<li><a class="reference internal" href="#">Application Structure and Lifecycle</a><ul>
|
||||
<li><a class="reference internal" href="#application-setup">Application Setup</a></li>
|
||||
<li><a class="reference internal" href="#serving-the-application">Serving the Application</a><ul>
|
||||
<li><a class="reference internal" href="#middleware">Middleware</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
<li><a class="reference internal" href="#how-a-request-is-handled">How a Request is Handled</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
</ul>
|
||||
|
||||
<h3>Navigation</h3>
|
||||
<ul>
|
||||
<li><a href="index.html">Overview</a>
|
||||
<ul>
|
||||
<li>Previous: <a href="views.html" title="previous chapter">Class-based Views</a>
|
||||
<li>Next: <a href="appcontext.html" title="next chapter">The Application Context</a>
|
||||
</ul>
|
||||
</li>
|
||||
</ul>
|
||||
<search id="searchbox" style="display: none" role="search">
|
||||
<h3 id="searchlabel">Quick search</h3>
|
||||
<div class="searchformwrapper">
|
||||
|
|
@ -468,4 +254,4 @@ method, this part of the documentation is for you.</p>
|
|||
Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 8.1.3.
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
</html>
|
||||
|
|
|
|||
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