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<title>Large Applications as Packages — Flask Documentation (3.2.x)</title>
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<title>SQLAlchemy in Flask — Flask Documentation (3.2.x)</title>
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<link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=6625fa76" />
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@ -15,8 +15,8 @@
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<link rel="next" title="Application Factories" href="appfactories.html" />
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<h3>Navigation</h3>
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<a href="../py-modindex.html" title="Python Module Index"
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>modules</a> |</li>
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<li class="right" >
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<a href="appfactories.html" title="Application Factories"
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accesskey="N">next</a> |</li>
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<li class="right" >
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<a href="index.html" title="Patterns for Flask"
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<a href="sqlite3.html" title="Using SQLite 3 with Flask"
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accesskey="P">previous</a> |</li>
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<li class="nav-item nav-item-0"><a href="../index.html">Flask Documentation (3.2.x)</a> »</li>
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<li class="nav-item nav-item-1"><a href="index.html" accesskey="U">Patterns for Flask</a> »</li>
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<li class="nav-item nav-item-this"><a href="">Large Applications as Packages</a></li>
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<li class="nav-item nav-item-this"><a href="">SQLAlchemy in Flask</a></li>
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<div class="bodywrapper">
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<div class="body" role="main">
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<section id="large-applications-as-packages">
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<h1>Large Applications as Packages<a class="headerlink" href="#large-applications-as-packages" title="Link to this heading">¶</a></h1>
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<p>Imagine a simple flask application structure that looks like this:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">/</span><span class="n">yourapplication</span>
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<span class="n">yourapplication</span><span class="o">.</span><span class="n">py</span>
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<span class="o">/</span><span class="n">static</span>
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<span class="n">style</span><span class="o">.</span><span class="n">css</span>
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<span class="o">/</span><span class="n">templates</span>
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<span class="n">layout</span><span class="o">.</span><span class="n">html</span>
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<span class="n">index</span><span class="o">.</span><span class="n">html</span>
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<span class="n">login</span><span class="o">.</span><span class="n">html</span>
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<span class="o">...</span>
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</pre></div>
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</div>
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<p>While this is fine for small applications, for larger applications
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it’s a good idea to use a package instead of a module.
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The <a class="reference internal" href="../tutorial/index.html"><span class="doc">Tutorial</span></a> is structured to use the package pattern,
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see the <a class="reference external" href="https://github.com/pallets/flask/tree/main/examples/tutorial">example code</a>.</p>
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<section id="simple-packages">
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<h2>Simple Packages<a class="headerlink" href="#simple-packages" title="Link to this heading">¶</a></h2>
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<p>To convert that into a larger one, just create a new folder
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<code class="file docutils literal notranslate"><span class="pre">yourapplication</span></code> inside the existing one and move everything below it.
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Then rename <code class="file docutils literal notranslate"><span class="pre">yourapplication.py</span></code> to <code class="file docutils literal notranslate"><span class="pre">__init__.py</span></code>. (Make sure to delete
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all <code class="docutils literal notranslate"><span class="pre">.pyc</span></code> files first, otherwise things would most likely break)</p>
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<p>You should then end up with something like that:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">/</span><span class="n">yourapplication</span>
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<span class="o">/</span><span class="n">yourapplication</span>
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<span class="fm">__init__</span><span class="o">.</span><span class="n">py</span>
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<span class="o">/</span><span class="n">static</span>
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<span class="n">style</span><span class="o">.</span><span class="n">css</span>
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<span class="o">/</span><span class="n">templates</span>
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<span class="n">layout</span><span class="o">.</span><span class="n">html</span>
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<span class="n">index</span><span class="o">.</span><span class="n">html</span>
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<span class="n">login</span><span class="o">.</span><span class="n">html</span>
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<span class="o">...</span>
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</pre></div>
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</div>
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<p>But how do you run your application now? The naive <code class="docutils literal notranslate"><span class="pre">python</span>
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<span class="pre">yourapplication/__init__.py</span></code> will not work. Let’s just say that Python
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does not want modules in packages to be the startup file. But that is not
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a big problem, just add a new file called <code class="file docutils literal notranslate"><span class="pre">pyproject.toml</span></code> next to the inner
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<code class="file docutils literal notranslate"><span class="pre">yourapplication</span></code> folder with the following contents:</p>
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<div class="highlight-toml notranslate"><div class="highlight"><pre><span></span><span class="k">[project]</span>
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<span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s2">"yourapplication"</span>
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<span class="n">dependencies</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">[</span>
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<span class="w"> </span><span class="s2">"flask"</span><span class="p">,</span>
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<span class="p">]</span>
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<span class="k">[build-system]</span>
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<span class="n">requires</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">[</span><span class="s2">"flit_core<4"</span><span class="p">]</span>
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<span class="n">build-backend</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s2">"flit_core.buildapi"</span>
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</pre></div>
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</div>
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<p>Install your application so it is importable:</p>
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<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>$ pip install -e .
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</pre></div>
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</div>
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<p>To use the <code class="docutils literal notranslate"><span class="pre">flask</span></code> command and run your application you need to set
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the <code class="docutils literal notranslate"><span class="pre">--app</span></code> option that tells Flask where to find the application
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instance:</p>
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<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>$ flask --app yourapplication run
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</pre></div>
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</div>
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<p>What did we gain from this? Now we can restructure the application a bit
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into multiple modules. The only thing you have to remember is the
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following quick checklist:</p>
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<ol class="arabic simple">
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<li><p>the <code class="code docutils literal notranslate"><span class="pre">Flask</span></code> application object creation has to be in the
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<code class="file docutils literal notranslate"><span class="pre">__init__.py</span></code> file. That way each module can import it safely and the
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<code class="code docutils literal notranslate"><span class="pre">__name__</span></code> variable will resolve to the correct package.</p></li>
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<li><p>all the view functions (the ones with a <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>
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||||
decorator on top) have to be imported in the <code class="file docutils literal notranslate"><span class="pre">__init__.py</span></code> file.
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Not the object itself, but the module it is in. Import the view module
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<strong>after the application object is created</strong>.</p></li>
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</ol>
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<p>Here’s an example <code class="file docutils literal notranslate"><span class="pre">__init__.py</span></code>:</p>
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<div class="highlight-default 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>
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<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>
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<section id="sqlalchemy-in-flask">
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<h1>SQLAlchemy in Flask<a class="headerlink" href="#sqlalchemy-in-flask" title="Link to this heading">¶</a></h1>
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<p>Many people prefer <a class="reference external" href="https://www.sqlalchemy.org/">SQLAlchemy</a> for database access. In this case it’s
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encouraged to use a package instead of a module for your flask application
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and drop the models into a separate module (<a class="reference internal" href="packages.html"><span class="doc">Large Applications as Packages</span></a>). While that
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is not necessary, it makes a lot of sense.</p>
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<p>There are four very common ways to use SQLAlchemy. I will outline each
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of them here:</p>
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<section id="flask-sqlalchemy-extension">
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<h2>Flask-SQLAlchemy Extension<a class="headerlink" href="#flask-sqlalchemy-extension" title="Link to this heading">¶</a></h2>
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<p>Because SQLAlchemy is a common database abstraction layer and object
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relational mapper that requires a little bit of configuration effort,
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there is a Flask extension that handles that for you. This is recommended
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if you want to get started quickly.</p>
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<p>You can download <a class="reference external" href="https://flask-sqlalchemy.palletsprojects.com/">Flask-SQLAlchemy</a> from <a class="reference external" href="https://pypi.org/project/Flask-SQLAlchemy/">PyPI</a>.</p>
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</section>
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<section id="declarative">
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<h2>Declarative<a class="headerlink" href="#declarative" title="Link to this heading">¶</a></h2>
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<p>The declarative extension in SQLAlchemy is the most recent method of using
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SQLAlchemy. It allows you to define tables and models in one go, similar
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to how Django works. In addition to the following text I recommend the
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official documentation on the <a class="reference external" href="https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/">declarative</a> extension.</p>
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<p>Here’s the example <code class="file docutils literal notranslate"><span class="pre">database.py</span></code> module for your application:</p>
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||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">create_engine</span>
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<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy.orm</span><span class="w"> </span><span class="kn">import</span> <span class="n">scoped_session</span><span class="p">,</span> <span class="n">sessionmaker</span><span class="p">,</span> <span class="n">declarative_base</span>
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<span class="kn">import</span><span class="w"> </span><span class="nn">yourapplication.views</span>
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</pre></div>
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</div>
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<p>And this is what <code class="file docutils literal notranslate"><span class="pre">views.py</span></code> would look like:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication</span><span class="w"> </span><span class="kn">import</span> <span class="n">app</span>
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<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s1">'sqlite:////tmp/test.db'</span><span class="p">)</span>
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||||
<span class="n">db_session</span> <span class="o">=</span> <span class="n">scoped_session</span><span class="p">(</span><span class="n">sessionmaker</span><span class="p">(</span><span class="n">autocommit</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
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<span class="n">autoflush</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
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<span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">))</span>
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<span class="n">Base</span> <span class="o">=</span> <span class="n">declarative_base</span><span class="p">()</span>
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<span class="n">Base</span><span class="o">.</span><span class="n">query</span> <span class="o">=</span> <span class="n">db_session</span><span class="o">.</span><span class="n">query_property</span><span class="p">()</span>
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<span class="nd">@app</span><span class="o">.</span><span class="n">route</span><span class="p">(</span><span class="s1">'/'</span><span class="p">)</span>
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<span class="k">def</span><span class="w"> </span><span class="nf">index</span><span class="p">():</span>
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<span class="k">return</span> <span class="s1">'Hello World!'</span>
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<span class="k">def</span><span class="w"> </span><span class="nf">init_db</span><span class="p">():</span>
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<span class="c1"># import all modules here that might define models so that</span>
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<span class="c1"># they will be registered properly on the metadata. Otherwise</span>
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<span class="c1"># you will have to import them first before calling init_db()</span>
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<span class="kn">import</span><span class="w"> </span><span class="nn">yourapplication.models</span>
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<span class="n">Base</span><span class="o">.</span><span class="n">metadata</span><span class="o">.</span><span class="n">create_all</span><span class="p">(</span><span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">)</span>
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</pre></div>
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</div>
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<p>You should then end up with something like that:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">/</span><span class="n">yourapplication</span>
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<span class="n">pyproject</span><span class="o">.</span><span class="n">toml</span>
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<span class="o">/</span><span class="n">yourapplication</span>
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<span class="fm">__init__</span><span class="o">.</span><span class="n">py</span>
|
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<span class="n">views</span><span class="o">.</span><span class="n">py</span>
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||||
<span class="o">/</span><span class="n">static</span>
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||||
<span class="n">style</span><span class="o">.</span><span class="n">css</span>
|
||||
<span class="o">/</span><span class="n">templates</span>
|
||||
<span class="n">layout</span><span class="o">.</span><span class="n">html</span>
|
||||
<span class="n">index</span><span class="o">.</span><span class="n">html</span>
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<span class="n">login</span><span class="o">.</span><span class="n">html</span>
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<span class="o">...</span>
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<p>To define your models, just subclass the <code class="code docutils literal notranslate"><span class="pre">Base</span></code> class that was created by
|
||||
the code above. If you are wondering why we don’t have to care about
|
||||
threads here (like we did in the SQLite3 example above with the
|
||||
<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> object): that’s because SQLAlchemy does that for us
|
||||
already with the <a class="reference external" href="https://docs.sqlalchemy.org/en/20/orm/contextual.html#sqlalchemy.orm.scoped_session" title="(in SQLAlchemy v2.0)"><code class="xref py py-class docutils literal notranslate"><span class="pre">scoped_session</span></code></a>.</p>
|
||||
<p>To use SQLAlchemy in a declarative way with your application, you just
|
||||
have to put the following code into your application module. Flask will
|
||||
automatically remove database sessions at the end of the request or
|
||||
when the application shuts down:</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.database</span><span class="w"> </span><span class="kn">import</span> <span class="n">db_session</span>
|
||||
|
||||
<span class="nd">@app</span><span class="o">.</span><span class="n">teardown_appcontext</span>
|
||||
<span class="k">def</span><span class="w"> </span><span class="nf">shutdown_session</span><span class="p">(</span><span class="n">exception</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
|
||||
<span class="n">db_session</span><span class="o">.</span><span class="n">remove</span><span class="p">()</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<div class="admonition-circular-imports admonition">
|
||||
<p class="admonition-title">Circular Imports</p>
|
||||
<p>Every Python programmer hates them, and yet we just added some:
|
||||
circular imports (That’s when two modules depend on each other. In this
|
||||
case <code class="file docutils literal notranslate"><span class="pre">views.py</span></code> depends on <code class="file docutils literal notranslate"><span class="pre">__init__.py</span></code>). Be advised that this is a
|
||||
bad idea in general but here it is actually fine. The reason for this is
|
||||
that we are not actually using the views in <code class="file docutils literal notranslate"><span class="pre">__init__.py</span></code> and just
|
||||
ensuring the module is imported and we are doing that at the bottom of
|
||||
the file.</p>
|
||||
<p>Here is an example model (put this into <code class="file docutils literal notranslate"><span class="pre">models.py</span></code>, e.g.):</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">Column</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">String</span>
|
||||
<span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.database</span><span class="w"> </span><span class="kn">import</span> <span class="n">Base</span>
|
||||
|
||||
<span class="k">class</span><span class="w"> </span><span class="nc">User</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
|
||||
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s1">'users'</span>
|
||||
<span class="nb">id</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||||
<span class="n">name</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">),</span> <span class="n">unique</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||||
<span class="n">email</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">String</span><span class="p">(</span><span class="mi">120</span><span class="p">),</span> <span class="n">unique</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||||
|
||||
<span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">email</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
|
||||
<span class="bp">self</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="n">name</span>
|
||||
<span class="bp">self</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="n">email</span>
|
||||
|
||||
<span class="k">def</span><span class="w"> </span><span class="fm">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||||
<span class="k">return</span> <span class="sa">f</span><span class="s1">'<User </span><span class="si">{</span><span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="si">!r}</span><span class="s1">>'</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>To create the database you can use the <code class="code docutils literal notranslate"><span class="pre">init_db</span></code> function:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.database</span><span class="w"> </span><span class="kn">import</span> <span class="n">init_db</span>
|
||||
<span class="gp">>>> </span><span class="n">init_db</span><span class="p">()</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>You can insert entries into the database like this:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.database</span><span class="w"> </span><span class="kn">import</span> <span class="n">db_session</span>
|
||||
<span class="gp">>>> </span><span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.models</span><span class="w"> </span><span class="kn">import</span> <span class="n">User</span>
|
||||
<span class="gp">>>> </span><span class="n">u</span> <span class="o">=</span> <span class="n">User</span><span class="p">(</span><span class="s1">'admin'</span><span class="p">,</span> <span class="s1">'admin@localhost'</span><span class="p">)</span>
|
||||
<span class="gp">>>> </span><span class="n">db_session</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">u</span><span class="p">)</span>
|
||||
<span class="gp">>>> </span><span class="n">db_session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>Querying is simple as well:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">User</span><span class="o">.</span><span class="n">query</span><span class="o">.</span><span class="n">all</span><span class="p">()</span>
|
||||
<span class="go">[<User 'admin'>]</span>
|
||||
<span class="gp">>>> </span><span class="n">User</span><span class="o">.</span><span class="n">query</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">User</span><span class="o">.</span><span class="n">name</span> <span class="o">==</span> <span class="s1">'admin'</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
|
||||
<span class="go"><User 'admin'></span>
|
||||
</pre></div>
|
||||
</div>
|
||||
</section>
|
||||
<section id="working-with-blueprints">
|
||||
<h2>Working with Blueprints<a class="headerlink" href="#working-with-blueprints" title="Link to this heading">¶</a></h2>
|
||||
<p>If you have larger applications it’s recommended to divide them into
|
||||
smaller groups where each group is implemented with the help of a
|
||||
blueprint. For a gentle introduction into this topic refer to the
|
||||
<a class="reference internal" href="../blueprints.html"><span class="doc">Modular Applications with Blueprints</span></a> chapter of the documentation.</p>
|
||||
<section id="manual-object-relational-mapping">
|
||||
<h2>Manual Object Relational Mapping<a class="headerlink" href="#manual-object-relational-mapping" title="Link to this heading">¶</a></h2>
|
||||
<p>Manual object relational mapping has a few upsides and a few downsides
|
||||
versus the declarative approach from above. The main difference is that
|
||||
you define tables and classes separately and map them together. It’s more
|
||||
flexible but a little more to type. In general it works like the
|
||||
declarative approach, so make sure to also split up your application into
|
||||
multiple modules in a package.</p>
|
||||
<p>Here is an example <code class="file docutils literal notranslate"><span class="pre">database.py</span></code> module for your application:</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">create_engine</span><span class="p">,</span> <span class="n">MetaData</span>
|
||||
<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy.orm</span><span class="w"> </span><span class="kn">import</span> <span class="n">scoped_session</span><span class="p">,</span> <span class="n">sessionmaker</span>
|
||||
|
||||
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s1">'sqlite:////tmp/test.db'</span><span class="p">)</span>
|
||||
<span class="n">metadata</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">()</span>
|
||||
<span class="n">db_session</span> <span class="o">=</span> <span class="n">scoped_session</span><span class="p">(</span><span class="n">sessionmaker</span><span class="p">(</span><span class="n">autocommit</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
|
||||
<span class="n">autoflush</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span>
|
||||
<span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">))</span>
|
||||
<span class="k">def</span><span class="w"> </span><span class="nf">init_db</span><span class="p">():</span>
|
||||
<span class="n">metadata</span><span class="o">.</span><span class="n">create_all</span><span class="p">(</span><span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">)</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>As in the declarative approach, you need to close the session after
|
||||
each request or application context shutdown. Put this into your
|
||||
application module:</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.database</span><span class="w"> </span><span class="kn">import</span> <span class="n">db_session</span>
|
||||
|
||||
<span class="nd">@app</span><span class="o">.</span><span class="n">teardown_appcontext</span>
|
||||
<span class="k">def</span><span class="w"> </span><span class="nf">shutdown_session</span><span class="p">(</span><span class="n">exception</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
|
||||
<span class="n">db_session</span><span class="o">.</span><span class="n">remove</span><span class="p">()</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>Here is an example table and model (put this into <code class="file docutils literal notranslate"><span class="pre">models.py</span></code>):</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">Table</span><span class="p">,</span> <span class="n">Column</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">String</span>
|
||||
<span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy.orm</span><span class="w"> </span><span class="kn">import</span> <span class="n">mapper</span>
|
||||
<span class="kn">from</span><span class="w"> </span><span class="nn">yourapplication.database</span><span class="w"> </span><span class="kn">import</span> <span class="n">metadata</span><span class="p">,</span> <span class="n">db_session</span>
|
||||
|
||||
<span class="k">class</span><span class="w"> </span><span class="nc">User</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
|
||||
<span class="n">query</span> <span class="o">=</span> <span class="n">db_session</span><span class="o">.</span><span class="n">query_property</span><span class="p">()</span>
|
||||
|
||||
<span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">email</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
|
||||
<span class="bp">self</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="n">name</span>
|
||||
<span class="bp">self</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="n">email</span>
|
||||
|
||||
<span class="k">def</span><span class="w"> </span><span class="fm">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
|
||||
<span class="k">return</span> <span class="sa">f</span><span class="s1">'<User </span><span class="si">{</span><span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="si">!r}</span><span class="s1">>'</span>
|
||||
|
||||
<span class="n">users</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s1">'users'</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span>
|
||||
<span class="n">Column</span><span class="p">(</span><span class="s1">'id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="kc">True</span><span class="p">),</span>
|
||||
<span class="n">Column</span><span class="p">(</span><span class="s1">'name'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">50</span><span class="p">),</span> <span class="n">unique</span><span class="o">=</span><span class="kc">True</span><span class="p">),</span>
|
||||
<span class="n">Column</span><span class="p">(</span><span class="s1">'email'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="mi">120</span><span class="p">),</span> <span class="n">unique</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||||
<span class="p">)</span>
|
||||
<span class="n">mapper</span><span class="p">(</span><span class="n">User</span><span class="p">,</span> <span class="n">users</span><span class="p">)</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>Querying and inserting works exactly the same as in the example above.</p>
|
||||
</section>
|
||||
<section id="sql-abstraction-layer">
|
||||
<h2>SQL Abstraction Layer<a class="headerlink" href="#sql-abstraction-layer" title="Link to this heading">¶</a></h2>
|
||||
<p>If you just want to use the database system (and SQL) abstraction layer
|
||||
you basically only need the engine:</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">create_engine</span><span class="p">,</span> <span class="n">MetaData</span><span class="p">,</span> <span class="n">Table</span>
|
||||
|
||||
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s1">'sqlite:////tmp/test.db'</span><span class="p">)</span>
|
||||
<span class="n">metadata</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">(</span><span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">)</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>Then you can either declare the tables in your code like in the examples
|
||||
above, or automatically load them:</p>
|
||||
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">Table</span>
|
||||
|
||||
<span class="n">users</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s1">'users'</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span> <span class="n">autoload</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>To insert data you can use the <code class="code docutils literal notranslate"><span class="pre">insert</span></code> method. We have to get a
|
||||
connection first so that we can use a transaction:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">con</span> <span class="o">=</span> <span class="n">engine</span><span class="o">.</span><span class="n">connect</span><span class="p">()</span>
|
||||
<span class="gp">>>> </span><span class="n">con</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="n">users</span><span class="o">.</span><span class="n">insert</span><span class="p">(),</span> <span class="n">name</span><span class="o">=</span><span class="s1">'admin'</span><span class="p">,</span> <span class="n">email</span><span class="o">=</span><span class="s1">'admin@localhost'</span><span class="p">)</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>SQLAlchemy will automatically commit for us.</p>
|
||||
<p>To query your database, you use the engine directly or use a connection:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">users</span><span class="o">.</span><span class="n">select</span><span class="p">(</span><span class="n">users</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">execute</span><span class="p">()</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
|
||||
<span class="go">(1, 'admin', 'admin@localhost')</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>These results are also dict-like tuples:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">r</span> <span class="o">=</span> <span class="n">users</span><span class="o">.</span><span class="n">select</span><span class="p">(</span><span class="n">users</span><span class="o">.</span><span class="n">c</span><span class="o">.</span><span class="n">id</span> <span class="o">==</span> <span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">execute</span><span class="p">()</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
|
||||
<span class="gp">>>> </span><span class="n">r</span><span class="p">[</span><span class="s1">'name'</span><span class="p">]</span>
|
||||
<span class="go">'admin'</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>You can also pass strings of SQL statements to the
|
||||
<code class="xref py py-meth docutils literal notranslate"><span class="pre">execute()</span></code> method:</p>
|
||||
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">engine</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s1">'select * from users where id = :1'</span><span class="p">,</span> <span class="p">[</span><span class="mi">1</span><span class="p">])</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
|
||||
<span class="go">(1, 'admin', 'admin@localhost')</span>
|
||||
</pre></div>
|
||||
</div>
|
||||
<p>For more information about SQLAlchemy, head over to the
|
||||
<a class="reference external" href="https://www.sqlalchemy.org/">website</a>.</p>
|
||||
</section>
|
||||
</section>
|
||||
|
||||
|
|
@ -177,18 +250,20 @@ blueprint. For a gentle introduction into this topic refer to the
|
|||
<span id="sidebar-top"></span>
|
||||
<div class="sphinxsidebar" role="navigation" aria-label="Main">
|
||||
<div class="sphinxsidebarwrapper">
|
||||
|
||||
|
||||
|
||||
|
||||
<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="#">Large Applications as Packages</a><ul>
|
||||
<li><a class="reference internal" href="#simple-packages">Simple Packages</a></li>
|
||||
<li><a class="reference internal" href="#working-with-blueprints">Working with Blueprints</a></li>
|
||||
<li><a class="reference internal" href="#">SQLAlchemy in Flask</a><ul>
|
||||
<li><a class="reference internal" href="#flask-sqlalchemy-extension">Flask-SQLAlchemy Extension</a></li>
|
||||
<li><a class="reference internal" href="#declarative">Declarative</a></li>
|
||||
<li><a class="reference internal" href="#manual-object-relational-mapping">Manual Object Relational Mapping</a></li>
|
||||
<li><a class="reference internal" href="#sql-abstraction-layer">SQL Abstraction Layer</a></li>
|
||||
</ul>
|
||||
</li>
|
||||
</ul>
|
||||
|
|
@ -198,8 +273,8 @@ blueprint. For a gentle introduction into this topic refer to the
|
|||
<ul>
|
||||
<li><a href="index.html">Patterns for Flask</a>
|
||||
<ul>
|
||||
<li>Previous: <a href="index.html" title="previous chapter">Patterns for Flask</a>
|
||||
<li>Next: <a href="appfactories.html" title="next chapter">Application Factories</a></ul>
|
||||
<li>Previous: <a href="sqlite3.html" title="previous chapter">Using SQLite 3 with Flask</a>
|
||||
<li>Next: <a href="fileuploads.html" title="next chapter">Uploading Files</a></ul>
|
||||
</li>
|
||||
</ul>
|
||||
</li>
|
||||
|
|
@ -223,4 +298,4 @@ blueprint. For a gentle introduction into this topic refer to the
|
|||
Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 8.1.3.
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
</html>
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue