The templating language is fairly simple, just {{stuff}}.  For
example::

    >>> from paste.util.template import Template, sub
    >>> sub('Hi {{name}}', name='Ian')
    'Hi Ian'
    >>> Template('Hi {{repr(name)}}').substitute(name='Ian')
    "Hi 'Ian'"
    >>> Template('Hi {{name+1}}').substitute(name='Ian')  # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
        ...
    TypeError: cannot concatenate 'str' and 'int' objects at line 1 column 6

It also has Django-style piping::

    >>> sub('Hi {{name|repr}}', name='Ian')
    "Hi 'Ian'"

Note that None shows up as an empty string::

    >>> sub('Hi {{name}}', name=None)
    'Hi '

And if/elif/else::

    >>> t = Template('{{if x}}{{y}}{{else}}{{z}}{{endif}}')
    >>> t.substitute(x=1, y=2, z=3)
    '2'
    >>> t.substitute(x=0, y=2, z=3)
    '3'
    >>> t = Template('{{if x > 0}}positive{{elif x < 0}}negative{{else}}zero{{endif}}')
    >>> t.substitute(x=1), t.substitute(x=-10), t.substitute(x=0)
    ('positive', 'negative', 'zero')

Plus a for loop::

    >>> t = Template('{{for i in x}}i={{i}}\n{{endfor}}')
    >>> t.substitute(x=range(3))
    'i=0\ni=1\ni=2\n'
    >>> t = Template('{{for a, b in sorted(z.items()):}}{{a}}={{b}},{{endfor}}')
    >>> t.substitute(z={1: 2, 3: 4})
    '1=2,3=4,'
    >>> t = Template('{{for i in x}}{{if not i}}{{break}}'
    ...              '{{endif}}{{i}} {{endfor}}')
    >>> t.substitute(x=[1, 2, 0, 3, 4])
    '1 2 '
    >>> t = Template('{{for i in x}}{{if not i}}{{continue}}'
    ...              '{{endif}}{{i}} {{endfor}}')
    >>> t.substitute(x=[1, 2, 0, 3, 0, 4])
    '1 2 3 4 '

Also Python blocks::

    >>> sub('{{py:\nx=1\n}}{{x}}')
    '1'

And some syntax errors::

    >>> t = Template('{{if x}}', name='foo.html')
    Traceback (most recent call last):
        ...
    TemplateError: No {{endif}} at line 1 column 3 in foo.html
    >>> t = Template('{{for x}}', name='foo2.html')
    Traceback (most recent call last):
        ...
    TemplateError: Bad for (no "in") in 'x' at line 1 column 3 in foo2.html

There's also an HTMLTemplate that uses HTMLisms::

    >>> from paste.util.template import HTMLTemplate, sub_html, html
    >>> sub_html('hi {{name}}', name='<foo>')
    'hi &lt;foo&gt;'

But if you don't want quoting to happen you can do::

    >>> sub_html('hi {{name}}', name=html('<foo>'))
    'hi <foo>'
    >>> sub_html('hi {{name|html}}', name='<foo>')
    'hi <foo>'

Also a couple handy functions;:

    >>> t = HTMLTemplate('<a href="article?id={{id|url}}" {{attr(class_=class_)}}>')
    >>> t.substitute(id=1, class_='foo')
    '<a href="article?id=1" class="foo">'
    >>> t.substitute(id='with space', class_=None)
    '<a href="article?id=with%20space" >'

There's a handyish looper thing you can also use in your templates (or
in Python, but it's more useful in templates generally)::

    >>> from paste.util.looper import looper
    >>> seq = ['apple', 'asparagus', 'Banana', 'orange']
    >>> for loop, item in looper(seq):
    ...     if item == 'apple':
    ...         assert loop.first
    ...     elif item == 'orange':
    ...         assert loop.last
    ...     if loop.first_group(lambda i: i[0].upper()):
    ...         print('%s:' % item[0].upper())
    ...     print("%s %s" % (loop.number, item))
    A:
    1 apple
    2 asparagus
    B:
    3 Banana
    O:
    4 orange

It will also strip out empty lines, when there is a line that only
contains a directive/statement (if/for, etc)::

    >>> sub('{{if 1}}\n{{x}}\n{{endif}}\n', x=0)
    '0\n'
    >>> sub('{{if 1}}x={{x}}\n{{endif}}\n', x=1)
    'x=1\n'
    >>> sub('{{if 1}}\nx={{x}}\n{{endif}}\n', x=1)
    'x=1\n'

Lastly, there is a special directive that will create a default value
for a variable, if no value is given::

    >>> sub('{{default x=1}}{{x}}', x=2)
    '2'
    >>> sub('{{default x=1}}{{x}}')
    '1'
    >>> # The normal case:
    >>> sub('{{x}}')  # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
        ...
    NameError: name 'x' is not defined at line 1 column 3

And comments work::

    >>> sub('Test=x{{#whatever}}')
    'Test=x'
