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diff --git a/app/static/doc/flask-docs/patterns/streaming.html b/app/static/doc/flask-docs/patterns/streaming.html new file mode 100644 index 0000000..9285ec4 --- /dev/null +++ b/app/static/doc/flask-docs/patterns/streaming.html @@ -0,0 +1,172 @@ + +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> + + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> + + <title>Streaming Contents — Flask 0.8 documentation</title> + + <link rel="stylesheet" href="../_static/flasky.css" type="text/css" /> + <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> + + <script type="text/javascript"> + var DOCUMENTATION_OPTIONS = { + URL_ROOT: '../', + VERSION: '0.8', + COLLAPSE_INDEX: false, + FILE_SUFFIX: '.html', + HAS_SOURCE: true + }; + </script> + <script type="text/javascript" src="../_static/jquery.js"></script> + <script type="text/javascript" src="../_static/underscore.js"></script> + <script type="text/javascript" src="../_static/doctools.js"></script> + <link rel="top" title="Flask 0.8 documentation" href="../index.html" /> + <link rel="up" title="Patterns for Flask" href="index.html" /> + <link rel="next" title="Deferred Request Callbacks" href="deferredcallbacks.html" /> + <link rel="prev" title="Adding a favicon" href="favicon.html" /> + + + <link rel="apple-touch-icon" href="../_static/touch-icon.png" /> + + <link media="only screen and (max-device-width: 480px)" href="../_static/small_flask.css" type= "text/css" rel="stylesheet" /> + + </head> + <body> + <div class="related"> + <h3>Navigation</h3> + <ul> + <li class="right" style="margin-right: 10px"> + <a href="../genindex.html" title="General Index" + accesskey="I">index</a></li> + <li class="right" > + <a href="deferredcallbacks.html" title="Deferred Request Callbacks" + accesskey="N">next</a> |</li> + <li class="right" > + <a href="favicon.html" title="Adding a favicon" + accesskey="P">previous</a> |</li> + <li><a href="../index.html">Flask 0.8 documentation</a> »</li> + <li><a href="index.html" accesskey="U">Patterns for Flask</a> »</li> + </ul> + </div> + + <div class="document"> + <div class="documentwrapper"> + <div class="bodywrapper"> + <div class="body"> + + <div class="section" id="streaming-contents"> +<h1>Streaming Contents<a class="headerlink" href="#streaming-contents" title="Permalink to this headline">¶</a></h1> +<p>Sometimes you want to send an enormous amount of data to the client, much +more than you want to keep in memory. When you are generating the data on +the fly though, how do you send that back to the client without the +roundtrip to the filesystem?</p> +<p>The answer is by using generators and direct responses.</p> +<div class="section" id="basic-usage"> +<h2>Basic Usage<a class="headerlink" href="#basic-usage" title="Permalink to this headline">¶</a></h2> +<p>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 +data and to then invoke that function and pass it to a response object:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">flask</span> <span class="kn">import</span> <span class="n">Response</span> + +<span class="nd">@app.route</span><span class="p">(</span><span class="s">'/large.csv'</span><span class="p">)</span> +<span class="k">def</span> <span class="nf">generate_large_csv</span><span class="p">():</span> + <span class="k">def</span> <span class="nf">generate</span><span class="p">():</span> + <span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">iter_all_rows</span><span class="p">():</span> + <span class="k">yield</span> <span class="s">','</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">row</span><span class="p">)</span> <span class="o">+</span> <span class="s">'</span><span class="se">\n</span><span class="s">'</span> + <span class="k">return</span> <span class="n">Response</span><span class="p">(</span><span class="n">generate</span><span class="p">(),</span> <span class="n">mimetype</span><span class="o">=</span><span class="s">'text/csv'</span><span class="p">)</span> +</pre></div> +</div> +<p>Each <tt class="docutils literal"><span class="pre">yield</span></tt> expression is directly sent to the browser. Now though +that some WSGI middlewares might break streaming, so be careful there in +debug environments with profilers and other things you might have enabled.</p> +</div> +<div class="section" id="streaming-from-templates"> +<h2>Streaming from Templates<a class="headerlink" href="#streaming-from-templates" title="Permalink to this headline">¶</a></h2> +<p>The Jinja2 template engine also supports rendering templates piece by +piece. This functionality is not directly exposed by Flask because it is +quite uncommon, but you can easily do it yourself:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">flask</span> <span class="kn">import</span> <span class="n">Response</span> + +<span class="k">def</span> <span class="nf">stream_template</span><span class="p">(</span><span class="n">template_name</span><span class="p">,</span> <span class="o">**</span><span class="n">context</span><span class="p">):</span> + <span class="n">app</span><span class="o">.</span><span class="n">update_template_context</span><span class="p">(</span><span class="n">context</span><span class="p">)</span> + <span class="n">t</span> <span class="o">=</span> <span class="n">app</span><span class="o">.</span><span class="n">jinja_env</span><span class="o">.</span><span class="n">get_template</span><span class="p">(</span><span class="n">template_name</span><span class="p">)</span> + <span class="n">rv</span> <span class="o">=</span> <span class="n">t</span><span class="o">.</span><span class="n">stream</span><span class="p">(</span><span class="n">context</span><span class="p">)</span> + <span class="n">rv</span><span class="o">.</span><span class="n">enable_buffering</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> + <span class="k">return</span> <span class="n">rv</span> + +<span class="nd">@app.route</span><span class="p">(</span><span class="s">'/my-large-page.html'</span><span class="p">)</span> +<span class="k">def</span> <span class="nf">render_large_template</span><span class="p">():</span> + <span class="n">rows</span> <span class="o">=</span> <span class="n">iter_all_rows</span><span class="p">()</span> + <span class="k">return</span> <span class="n">Response</span><span class="p">(</span><span class="n">stream_template</span><span class="p">(</span><span class="s">'the_template.html'</span><span class="p">,</span> <span class="n">rows</span><span class="o">=</span><span class="n">rows</span><span class="p">))</span> +</pre></div> +</div> +<p>The trick here is to get the template object from the Jinja2 environment +on the application and to call <tt class="xref py py-meth docutils literal"><span class="pre">stream()</span></tt> instead of +<tt class="xref py py-meth docutils literal"><span class="pre">render()</span></tt> which returns a stream object instead of a +string. Since we’re bypassing the Flask template render functions and +using the template object itself we have to make sure to update the render +context ourselves by calling <a class="reference internal" href="../api.html#flask.Flask.update_template_context" title="flask.Flask.update_template_context"><tt class="xref py py-meth docutils literal"><span class="pre">update_template_context()</span></tt></a>. +The template is then evaluated as the stream is iterated over. Since each +time you do a yield the server will flush the content to the client you +might want to buffer up a few items in the template which you can do with +<tt class="docutils literal"><span class="pre">rv.enable_buffering(size)</span></tt>. <tt class="docutils literal"><span class="pre">5</span></tt> is a sane default.</p> +</div> +</div> + + + </div> + </div> + </div> + <div class="sphinxsidebar"> + <div class="sphinxsidebarwrapper"><p class="logo"><a href="../index.html"> + <img class="logo" src="../_static/flask.png" alt="Logo"/> +</a></p> + <h3><a href="../index.html">Table Of Contents</a></h3> + <ul> +<li><a class="reference internal" href="#">Streaming Contents</a><ul> +<li><a class="reference internal" href="#basic-usage">Basic Usage</a></li> +<li><a class="reference internal" href="#streaming-from-templates">Streaming from Templates</a></li> +</ul> +</li> +</ul> +<h3>Related Topics</h3> +<ul> + <li><a href="../index.html">Documentation overview</a><ul> + <li><a href="index.html">Patterns for Flask</a><ul> + <li>Previous: <a href="favicon.html" title="previous chapter">Adding a favicon</a></li> + <li>Next: <a href="deferredcallbacks.html" title="next chapter">Deferred Request Callbacks</a></li> + </ul></li> + </ul></li> +</ul> + <h3>This Page</h3> + <ul class="this-page-menu"> + <li><a href="../_sources/patterns/streaming.txt" + rel="nofollow">Show Source</a></li> + </ul> +<div id="searchbox" style="display: none"> + <h3>Quick search</h3> + <form class="search" action="../search.html" method="get"> + <input type="text" name="q" /> + <input type="submit" value="Go" /> + <input type="hidden" name="check_keywords" value="yes" /> + <input type="hidden" name="area" value="default" /> + </form> + <p class="searchtip" style="font-size: 90%"> + Enter search terms or a module, class or function name. + </p> +</div> +<script type="text/javascript">$('#searchbox').show(0);</script> + </div> + </div> + <div class="clearer"></div> + </div> + <div class="footer"> + © Copyright 2010, Armin Ronacher. + Created using <a href="http://sphinx.pocoo.org/">Sphinx</a>. + </div> + </body> +</html>
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