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[docs] streaming contents: use app.response_class

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Examples should use app.response_class to encourage code that doesn't need to be changed should the response class be customized later on.
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iomintz 2020-06-17 22:00:35 -05:00 • committed by GitHub
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docs/patterns/streaming.rst
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@ -15,14 +15,12 @@ This is a basic view function that generates a lot of CSV data on the fly.
The trick is to have an inner function that uses a generator to generate The trick is to have an inner function that uses a generator to generate
data and to then invoke that function and pass it to a response object:: data and to then invoke that function and pass it to a response object::
from flask import Response
@app.route('/large.csv') @app.route('/large.csv')
def generate_large_csv(): def generate_large_csv():
def generate(): def generate():
for row in iter_all_rows(): for row in iter_all_rows():
yield f"{','.join(row)}\n" yield f"{','.join(row)}\n"
return Response(generate(), mimetype='text/csv') return app.response_class(generate(), mimetype='text/csv')
Each ``yield`` expression is directly sent to the browser. Note though Each ``yield`` expression is directly sent to the browser. Note though
that some WSGI middlewares might break streaming, so be careful there in that some WSGI middlewares might break streaming, so be careful there in
@ -35,8 +33,6 @@ The Jinja2 template engine also supports rendering templates piece by
piece. This functionality is not directly exposed by Flask because it is piece. This functionality is not directly exposed by Flask because it is
quite uncommon, but you can easily do it yourself:: quite uncommon, but you can easily do it yourself::
from flask import Response
def stream_template(template_name, **context): def stream_template(template_name, **context):
app.update_template_context(context) app.update_template_context(context)
t = app.jinja_env.get_template(template_name) t = app.jinja_env.get_template(template_name)
@ -47,7 +43,7 @@ quite uncommon, but you can easily do it yourself::
@app.route('/my-large-page.html') @app.route('/my-large-page.html')
def render_large_template(): def render_large_template():
rows = iter_all_rows() rows = iter_all_rows()
return Response(stream_template('the_template.html', rows=rows)) return app.response_class(stream_template('the_template.html', rows=rows))
The trick here is to get the template object from the Jinja2 environment The trick here is to get the template object from the Jinja2 environment
on the application and to call :meth:`~jinja2.Template.stream` instead of on the application and to call :meth:`~jinja2.Template.stream` instead of
@ -70,7 +66,7 @@ moment the function executes. Flask 0.9 provides you with a helper that
can keep the request context around during the execution of the can keep the request context around during the execution of the
generator:: generator::
from flask import stream_with_context, request, Response from flask import stream_with_context, request
@app.route('/stream') @app.route('/stream')
def streamed_response(): def streamed_response():
@ -78,7 +74,7 @@ generator::
yield 'Hello ' yield 'Hello '
yield request.args['name'] yield request.args['name']
yield '!' yield '!'
return Response(stream_with_context(generate())) return app.response_class(stream_with_context(generate()))
Without the :func:`~flask.stream_with_context` function you would get a Without the :func:`~flask.stream_with_context` function you would get a
:class:`RuntimeError` at that point. :class:`RuntimeError` at that point.