Werkzeug

Usage

In the application you can pass the Template class a string with the template code and then call render() (or substituate() for compatibility with string.Template) with either a dict or some keyword arguments to render the template:

from werkzeug import Template

tmpl = Template(u'''\
<h1>$escape(title)</h1>
<ul>
<% for href, caption in links %>
  <li><a href="$escape(href)">$escape(caption)</a></li>
<% endfor %>
</ul>''')

print tmpl.render(
    title='Foo',
    links=[
        ('/', 'Index'),
        ('/about', 'About')
    ]
)

This will then generate this:

<h1>Foo</h1>
<ul>
  <li><a href="/">Index</a></li>
  <li><a href="/about">About</a></li>
</ul>

You can also create templates from files:

t = Template.from_file('filename.html')

This also improves the error messages because then the python traceback system is able to locate the source for the error messages.

Template Syntax

The syntax elements are a mixture of django, genshi text and mod_python templates and used internally in werkzeug components.

We do not recommend using this template engine in a real environment because is quite slow and does not provide any advanced features. For simple applications (cgi script like) this can however be sufficient.

Printing Variables:

$variable
$variable.attribute[item](some, function)(calls)
${expression} or <%py print expression %>

Keep in mind that the print statement adds a newline after the call or a whitespace if it ends with a comma.

For Loops:

<% for item in seq %>
    ...
<% endfor %>

While Loops:

<% while expression %>
    <%py break / continue %>
<% endwhile %>

If Conditions:

<% if expression %>
    ...
<% elif expression %>
    ...
<% else %>
    ...
<% endif %>

Python Expressions:

<%py
    ...
%>

<%python
    ...
%>

Note on python expressions: You cannot start a loop in a python block and continue it in another one. This example does not work:

<%python
    for item in seq:
%>
    ...

Comments:

<%#
    This is a comment
%>

Missing Variables

If you try to access a missing variable you will get back an Undefined object. You can iterate over such an object or print it and it won't fail. However every other operation will raise an error. To test if a variable is undefined you can use this expression:

<% if variable is Undefined %>
    ...
<% endif %>

Global Functions

Beside the normal global functions and objects the following functions are added to every namespace: escape, url_encode, url_quote, and url_quote_plus. You can change those by subclassing Template and overriding the default_context dict:

class MyTemplate(Template):
    default_namespace = {
        'ueber_func':       ueber_func
    }
    # and now add the old functions too because they are useful
    default_namespace.update(Template.default_namespace)