pymstache 0.5.3

Mustache for Python

Pystache

Pystache is a Python implementation of Mustache. Mustache is a framework-agnostic, logic-free templating system inspired by ctemplate and et. Like ctemplate, Mustache “emphasizes separating logic from presentation: it is impossible to embed application logic in this template language.”

The mustache(5) man page provides a good introduction to Mustache’s syntax. For a more complete (and more current) description of Mustache’s behavior, see the official Mustache spec.

Pystache is semantically versioned and can be found on PyPI. This version of Pystache passes all tests in version 1.1.2 of the spec.

Requirements

Pystache is tested with–

• Python 2.4 (requires simplejson version 2.0.9 or earlier)

• Python 2.5 (requires simplejson)

• Python 2.6

• Python 2.7

• Python 3.1

• Python 3.2

• Python 3.3

• PyPy

Distribute (the setuptools fork) is recommended over setuptools, and is required in some cases (e.g. for Python 3 support). If you use pip, you probably already satisfy this requirement.

JSON support is needed only for the command-line interface and to run the spec tests. We require simplejson for earlier versions of Python since Python’s json module was added in Python 2.6.

For Python 2.4 we require an earlier version of simplejson since simplejson stopped officially supporting Python 2.4 in simplejson version 2.1.0. Earlier versions of simplejson can be installed manually, as follows:

pip install 'simplejson<2.1.0'

Official support for Python 2.4 will end with Pystache version 0.6.0.

Install It

pip install pystache

And test it–

pystache-test

To install and test from source (e.g. from GitHub), see the Develop section.

Use It

>>> import pystache
>>> print pystache.render('Hi {{person}}!', {'person': 'Mom'})
Hi Mom!

You can also create dedicated view classes to hold your view logic.

Here’s your view class (in …/examples/readme.py):

class SayHello(object):
    def to(self):
        return "Pizza"

Instantiating like so:

>>> from pystache.tests.examples.readme import SayHello
>>> hello = SayHello()

Then your template, say_hello.mustache (by default in the same directory as your class definition):

Hello, {{to}}!

Pull it together:

>>> renderer = pystache.Renderer()
>>> print renderer.render(hello)
Hello, Pizza!

For greater control over rendering (e.g. to specify a custom template directory), use the Renderer class like above. One can pass attributes to the Renderer class constructor or set them on a Renderer instance. To customize template loading on a per-view basis, subclass TemplateSpec. See the docstrings of the Renderer class and TemplateSpec class for more information.

You can also pre-parse a template:

>>> parsed = pystache.parse(u"Hey {{#who}}{{.}}!{{/who}}")
>>> print parsed
[u'Hey ', _SectionNode(key=u'who', index_begin=12, index_end=18, parsed=[_EscapeNode(key=u'.'), u'!'])]

And then:

>>> print renderer.render(parsed, {'who': 'Pops'})
Hey Pops!
>>> print renderer.render(parsed, {'who': 'you'})
Hey you!

Python 3

Pystache has supported Python 3 since version 0.5.1. Pystache behaves slightly differently between Python 2 and 3, as follows:

• In Python 2, the default html-escape function cgi.escape() does not escape single quotes. In Python 3, the default escape function html.escape() does escape single quotes.

• In both Python 2 and 3, the string and file encodings default to sys.getdefaultencoding(). However, this function can return different values under Python 2 and 3, even when run from the same system. Check your own system for the behavior on your system, or do not rely on the defaults by passing in the encodings explicitly (e.g. to the Renderer class).

Unicode

This section describes how Pystache handles unicode, strings, and encodings.

Internally, Pystache uses only unicode strings (str in Python 3 and unicode in Python 2). For input, Pystache accepts both unicode strings and byte strings (bytes in Python 3 and str in Python 2). For output, Pystache’s template rendering methods return only unicode.

Pystache’s Renderer class supports a number of attributes to control how Pystache converts byte strings to unicode on input. These include the file_encoding, string_encoding, and decode_errors attributes.

The file_encoding attribute is the encoding the renderer uses to convert to unicode any files read from the file system. Similarly, string_encoding is the encoding the renderer uses to convert any other byte strings encountered during the rendering process into unicode (e.g. context values that are encoded byte strings).

The decode_errors attribute is what the renderer passes as the errors argument to Python’s built-in unicode-decoding function (str() in Python 3 and unicode() in Python 2). The valid values for this argument are strict, ignore, and replace.

Each of these attributes can be set via the Renderer class’s constructor using a keyword argument of the same name. See the Renderer class’s docstrings for further details. In addition, the file_encoding attribute can be controlled on a per-view basis by subclassing the TemplateSpec class. When not specified explicitly, these attributes default to values set in Pystache’s defaults module.

Develop

To test from a source distribution (without installing)–

python test_pystache.py

To test Pystache with multiple versions of Python (with a single command!), you can use tox:

pip install 'virtualenv<1.8'  # Version 1.8 dropped support for Python 2.4.
pip install 'tox<1.4'  # Version 1.4 dropped support for Python 2.4.
tox

If you do not have all Python versions listed in tox.ini–

tox -e py26,py32  # for example

The source distribution tests also include doctests and tests from the Mustache spec. To include tests from the Mustache spec in your test runs:

git submodule init
git submodule update

The test harness parses the spec’s (more human-readable) yaml files if PyYAML is present. Otherwise, it parses the json files. To install PyYAML–

pip install pyyaml

To run a subset of the tests, you can use nose:

pip install nose
nosetests --tests pystache/tests/test_context.py:GetValueTests.test_dictionary__key_present

Using Python 3 with Pystache from source

Pystache is written in Python 2 and must be converted to Python 3 prior to using it with Python 3. The installation process (and tox) do this automatically.

To convert the code to Python 3 manually (while using Python 3)–

python setup.py build

This writes the converted code to a subdirectory called build. By design, Python 3 builds cannot be created from Python 2.

To convert the code without using setup.py, you can use 2to3 as follows (two steps)–

2to3 --write --nobackups --no-diffs --doctests_only pystache
2to3 --write --nobackups --no-diffs pystache

This converts the code (and doctests) in place.

To import pystache from a source distribution while using Python 3, be sure that you are importing from a directory containing a converted version of the code (e.g. from the build directory after converting), and not from the original (unconverted) source directory. Otherwise, you will get a syntax error. You can help prevent this by not running the Python IDE from the project directory when importing Pystache while using Python 3.

Mailing List

There is a mailing list. Note that there is a bit of a delay between posting a message and seeing it appear in the mailing list archive.

Credits

>>> context = { 'author': 'Chris Wanstrath', 'maintainer': 'Chris Jerdonek' }
>>> print pystache.render("Author: {{author}}\nMaintainer: {{maintainer}}", context)
Author: Chris Wanstrath
Maintainer: Chris Jerdonek

Pystache logo by David Phillips is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

History

Note: Official support for Python 2.4 will end with Pystache version 0.6.0.

0.5.3 (2012-11-03)

• Added ability to customize string coercion (e.g. to have None render as '') (issue #130).

• Added Renderer.render_name() to render a template by name (issue #122).

• Added TemplateSpec.template_path to specify an absolute path to a template (issue #41).

• Added option of raising errors on missing tags/partials: Renderer(missing_tags='strict') (issue #110).

• Added support for finding and loading templates by file name in addition to by template name (issue #127). [xgecko]

• Added a parse() function that yields a printable, pre-compiled parse tree.

• Added support for rendering pre-compiled templates.

• Added Python 3.3 to the list of supported versions.

• Added support for PyPy (issue #125).

• Added support for Travis CI (issue #124). [msabramo]

• Bugfix: defaults.DELIMITERS can now be changed at runtime (issue #135). [bennoleslie]

• Bugfix: exceptions raised from a property are no longer swallowed when getting a key from a context stack (issue #110).

• Bugfix: lambda section values can now return non-ascii, non-unicode strings (issue #118).

• Bugfix: allow test_pystache.py and tox to pass when run from a downloaded sdist (i.e. without the spec test directory).

• Convert HISTORY and README files from reST to Markdown.

• More robust handling of byte strings in Python 3.

• Added Creative Commons license for David Phillips’s logo.

0.5.2 (2012-05-03)

• Added support for dot notation and version 1.1.2 of the spec (issue #99). [rbp]

• Missing partials now render as empty string per latest version of spec (issue #115).

• Bugfix: falsey values now coerced to strings using str().

• Bugfix: lambda return values for sections no longer pushed onto context stack (issue #113).

• Bugfix: lists of lambdas for sections were not rendered (issue #114).

0.5.1 (2012-04-24)

• Added support for Python 3.1 and 3.2.

• Added tox support to test multiple Python versions.

• Added test script entry point: pystache-test.

• Added __version__ package attribute.

• Test harness now supports both YAML and JSON forms of Mustache spec.

• Test harness no longer requires nose.

0.5.0 (2012-04-03)

This version represents a major rewrite and refactoring of the code base that also adds features and fixes many bugs. All functionality and nearly all unit tests have been preserved. However, some backwards incompatible changes to the API have been made.

Below is a selection of some of the changes (not exhaustive).

Highlights:

• Pystache now passes all tests in version 1.0.3 of the Mustache spec. [pvande]

• Removed View class: it is no longer necessary to subclass from View or from any other class to create a view.

• Replaced Template with Renderer class: template rendering behavior can be modified via the Renderer constructor or by setting attributes on a Renderer instance.

• Added TemplateSpec class: template rendering can be specified on a per-view basis by subclassing from TemplateSpec.

• Introduced separation of concerns and removed circular dependencies (e.g. between Template and View classes, cf. issue #13).

• Unicode now used consistently throughout the rendering process.

• Expanded test coverage: nosetests now runs doctests and ~105 test cases from the Mustache spec (increasing the number of tests from 56 to ~315).

• Added a rudimentary benchmarking script to gauge performance while refactoring.

• Extensive documentation added (e.g. docstrings).

Other changes:

• Added a command-line interface. [vrde]

• The main rendering class now accepts a custom partial loader (e.g. a dictionary) and a custom escape function.

• Non-ascii characters in str strings are now supported while rendering.

• Added string encoding, file encoding, and errors options for decoding to unicode.

• Removed the output encoding option.

• Removed the use of markupsafe.

Bug fixes:

• Context values no longer processed as template strings. [jakearchibald]

• Whitespace surrounding sections is no longer altered, per the spec. [heliodor]

• Zeroes now render correctly when using PyPy. [alex]

• Multline comments now permitted. [fczuardi]

• Extensionless template files are now supported.

• Passing **kwargs to Template() no longer modifies the context.

• Passing **kwargs to Template() with no context no longer raises an exception.

0.4.1 (2012-03-25)

• Added support for Python 2.4. [wangtz, jvantuyl]

0.4.0 (2011-01-12)

• Add support for nested contexts (within template and view)

• Add support for inverted lists

• Decoupled template loading

0.3.1 (2010-05-07)

• Fix package

0.3.0 (2010-05-03)

• View.template_path can now hold a list of path

• Add {{& blah}} as an alias for {{{ blah }}}

• Higher Order Sections

• Inverted sections

0.2.0 (2010-02-15)

• Bugfix: Methods returning False or None are not rendered

• Bugfix: Don’t render an empty string when a tag’s value is 0. [enaeseth]

• Add support for using non-callables as View attributes. [joshthecoder]

• Allow using View instances as attributes. [joshthecoder]

• Support for Unicode and non-ASCII-encoded bytestring output. [enaeseth]

• Template file encoding awareness. [enaeseth]

0.1.1 (2009-11-13)

• Ensure we’re dealing with strings, always

• Tests can be run by executing the test file directly

0.1.0 (2009-11-12)

• First release

License

Copyright (C) 2012 Chris Jerdonek. All rights reserved.

Copyright (c) 2009 Chris Wanstrath

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.