Foundations of Python Network Programming 978-1-4302-3004-5

CHAPTER 11 ■ WEB APPLICATIONS
Listing 11–2 also requires an accompanying template file, which is shown in Listing 11–3.
Listing 11–2. Rewriting the WSGI Application With a Framework
#!/usr/bin/env python
# Foundations of Python Network Programming - Chapter 11 - wsgi_app.py
# A simple web application built using the Bottle micro-framework.
import base64, bottle
bottle.debug(True)
app = bottle.Bottle()
@app.route('/encode')
@bottle.view('bottle_template.html')
def encode():
» mystring = bottle.request.GET.get('mystring')
» if mystring is None:
» » bottle.abort(400, 'This form requires a "mystring" parameter')
» return dict(mystring=mystring, myb=base64.b64encode(mystring))
@app.route('/')
@bottle.view('bottle_template.html')
def index():
» return dict(mystring=None)
bottle.run(app=app, host='localhost', port=8080)
In Listing 11–1, the attention was on the single incoming HTTP request, and the branches in our
logic explored all of the possible lifespans for that particular protocol request. Listing 11–2 changes the
focus to the pages that actually exist on the site and giving each of these pages reasonable behaviors. The
same tree of possibilities exists, but the tree exists implicitly thanks to the possible URLs defined in the
code, not because the programmer has written a large if statement.
Listing 11–3. The Template That Goes With Listing 11–2
%#!/usr/bin/env python
%# Foundations of Python Network Programming - Chapter 11 - bottle_template.py
%# The page template that goes with bottle_app.py.
%#
bottle_app.py
%if mystring is None:
» Welcome! Enter a string:
»
%else:
» {{mystring}} base64 encoded is: {{myb}}
» Return to the home page
%end
It might seem merely a pleasant convenience that we can use the Bottle SimpleTemplate to insert our
variables into a web page and know that they will be escaped correctly. But the truth is that templates
serve, just like schemes for URL dispatch, to re-orient our attention: instead of the resulting web page
existing in our minds as what will result when the strings in our program listing are finally concatenated,
we get to lay out its HTML intact, in order, and in a file that can actually take an .html extension and be
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