anytemplate 0.1.8

Library to abstract template engines and provide common APIs

About

This is a python library works as an abstraction layer for various python template engines and rendering libraries, and provide a few very simple and easily understandable APIs to render templates.

Also a CLI tool called anytemplate_cli is provided to render templates written in these template languages.

• Author: Satoru SATOH <[e-mail]>

• License: MIT

The following template engines are supported currently:

Name	Notes
string.Template	Always available as it’s included in python standard lib.
jinja2	Highest priory will be given and becomes default if found
mako
Cheetah	Cheetah3 is needed to use with python 3.x
pystache

Features

• Provides very simple and unified APIs for various template engines:

  • anytemplate.renders() to render given template string

  • anytemplate.render() to render given template file

• Can process template engine specific options:

  • anytemplate.render{s,} allow passing option parameters specific to each template rendering functions behind this library

  • anytemplate.find_engine() returns an ‘engine’ object to allow some more fine tunes of template engine specific customization by passing option parameters to them

• Provide a CLI tool called anytemplate_cli to process templates in command line

API Usage

API Examples

Call ‘anytemplate.renders’ to render given template strings like this:

result = anytemplate.renders("{{ x|default('aaa') }}", {'x': 'bbb'},
                             at_engine="jinja2")

The first parameter is a template string itself. And the second one is a dict or dict-like object which is generally called as ‘context’ object to instantiate templates. The third one, keyword parameter ‘at_engine’ is needed to find the appropriate template engine to render given template string. This keyword parameter is necessary because it’s very difficult and should be almost impossible for any template languages to detect correct template engine only by given template string itself.

If ‘at_engine’ is omitted, a template engine of highest priority is choosen. Only available template engines and libraries are enabled automatically in anytemplate, so that that engine will be vary in accordance with your environment. For example, ‘jinja2’ is the engine of highest priority in my development envrionment with all supported template engines and libraries installed:

In [6]: import anytemplate

In [7]: anytemplate.find_engine()   # It will return the highest priority one.
Out[7]: anytemplate.engines.jinja2.Engine

In [8]: anytemplate.find_engine().name()
Out[8]: 'jinja2'

It’s also possible to some option parameters specific to the template engine choosen with keyword parameters like this:

# 'strict_undefined' is a parameter for mako.template.Template.__init__().
result = anytemplate.renders("${x}", {'x': 'bbb'},
                             at_engine="mako",
                             strict_undefined=False)

For details such as generic option parameters list of ‘anytemplate.renders’, see its help:

In [20]: help(anytemplate.renders)
Help on function renders in module anytemplate.api:

renders(template_content, context=None, at_paths=None, at_encoding='UTF-8', at_engine=None, at_ask_missing=False, at_cls_args=None, **kwargs)
    Compile and render given template content and return the result string.

    :param template_content: Template content
    :param context: A dict or dict-like object to instantiate given
        template file
    :param at_paths: Template search paths
    :param at_encoding: Template encoding
    :param at_engine: Specify the name of template engine to use explicitly or
        None to find it automatically anyhow.
    :param at_cls_args: Arguments passed to instantiate template engine class
    :param kwargs: Keyword arguments passed to the template engine to
        render templates with specific features enabled.

    :return: Rendered string

In [21]:

Call ‘anytemplate.render’ to render given template file like this:

result1 = anytemplate.render("/path/to/a_template.tmpl", {'x': 'bbb'},
                             at_engine="mako")

The parameters are similar to the previous example except for the first one.

The first parameter is not a template string but a path of template file, may be relative or absolute path, or basename with template search paths (at_paths=[PATH_0, PATH_1, …]) given.

Some module wraps actual template engines in anytemplate supports automatic detection of the engine by file extensions of template files. For example, Jinja2 template files of which expected file extensions are ‘.j2’ or ‘.jinja2’ typically. So I made that such files are automatically detected as jinja2 template file and you don’t need to specify the engine by ‘at_engine’ parameter like this:

# 'jinaj2' template engine is automatically choosen because the extension
# of template file is '.j2'.
result = anytemplate.render("/path/to/a_template.j2", {'x': 'bbb'})

For details such as option parameters list of ‘anytemplate.render’, see its help:

In [21]: help(anytemplate.render)
Help on function render in module anytemplate.api:

render(filepath, context=None, at_paths=None, at_encoding='UTF-8', at_engine=None, at_ask_missing=False, at_cls_args=None, **kwargs)
    Compile and render given template file and return the result string.

    :param template: Template file path
    :param context: A dict or dict-like object to instantiate given
        template file
    :param at_paths: Template search paths
    :param at_encoding: Template encoding
    :param at_engine: Specify the name of template engine to use explicitly or
        None to find it automatically anyhow.
    :param at_cls_args: Arguments passed to instantiate template engine class
    :param kwargs: Keyword arguments passed to the template engine to
        render templates with specific features enabled.

    :return: Rendered string

In [22]:

CLI Usage

CLI help

ssato@localhost% PYTHONPATH=. python anytemplate/cli.py -h
Usage: anytemplate/cli.py [OPTION ...] TEMPLATE_FILE

Options:
  -h, --help            show this help message and exit
  -T TEMPLATE_PATHS, --template-path=TEMPLATE_PATHS
                        Template search path can be specified multiple times.
                        Note: Dir in which given template exists is always
                        included in the search paths (at the end of the path
                        list) regardless of this option.
  -C CONTEXTS, --context=CONTEXTS
                        Specify file path and optionally its filetype, to
                        provides context data to instantiate templates.  The
                        option argument's format is
                        [type:]<file_name_or_path_or_glob_pattern> ex. -C
                        json:common.json -C ./specific.yaml -C yaml:test.dat,
                        -C yaml:/etc/foo.d/*.conf
  -E ENGINE, --engine=ENGINE
                        Specify template engine name such as 'jinja2'
  -L, --list-engines    List supported template engines in your environment
  -o OUTPUT, --output=OUTPUT
                        Output filename [stdout]
  -v, --verbose         Verbose mode
  -q, --quiet           Quiet mode
ssato@localhost% cat examples/ctx.yml
xs:
  - name: Alice
  - name: Bob
  - name: John

ssato@localhost% cat examples/jinja2.j2
{% include "jinja2-incl.j2" %}
ssato@localhost% cat examples/jinja2-incl.j2
{# jinja2 example: #}
{% for x in xs if x.name -%}
{{ x.name }}
{% endfor %}
ssato@localhost% PYTHONPATH=. python anytemplate/cli.py -E jinja2 \
> -C examples/ctx.yml examples/jinja2.j2

Alice
Bob
John

ssato@localhost%

CLI Features

Multiple context files support to define template parameters

The CLI tool (anytemplate_cli) supports to load multiple context files in YAML or JSON or others to give template parameters with -C|–context option.

Loading and composing of context files are handled by my another python library called anyconfig (python-anyconfig) if installed and available on your system.

• anyconfig on PyPI: http://pypi.python.org/pypi/anyconfig/

• python-anyconfig on github: https://github.com/ssato/python-anyconfig

If anyconfig is not found on your system, only JSON context files are supported format of context files, by help of python standard json or simplejson library.

Template search paths

Template search paths are specified with -T|–template-path option of the CLI tool (anytemplate_cli). This is useful when using ‘include’ directive in templates; ex. -T .:templates/.

NOTE: The default search path will be [‘.’, dir_in_which_given_template_file_is] where templatedir is the directory in which the given template file exists if -T option is not given. And even if -T option is used, templatedir will be appended to that search paths at the end.

Build & Install

If you’re Fedora or Red Hat Enterprise Linux user, you can build and install [s]rpm by yourself:

$ python setup.py srpm && mock dist/python-anytemplate-<ver_dist>.src.rpm

or:

$ python setup.py rpm

or you can install pre-built RPMs from one of my copr repos, https://copr.fedorainfracloud.org/coprs/ssato/python-anyconfig/

# Fedora
$ sudo dnf copr enable ssato/python-anyconfig
$ sudo dnf install -y python-anytemplate   # or python3-anytemplate (python3 version)

# RHEL, CentOS
$ (cd /etc/yum.repos.d; sudo curl -O https://copr.fedorainfracloud.org/coprs/ssato/python-anyconfig/repo/epel-7/ssato-python-anyconfig-epel-7.repo)
$ sudo dnf install -y python-anytemplate   # or python3-anytemplate (python3 version)

Otherwise, try usual ways to build and/or install python modules such like ‘pip install git+https://github.com/ssato/python-anytemplate’ and ‘python setup.py bdist’, etc.

Hacking

How to test

I choose tox for manual tests and CI. Try to run ‘tox [-e py27]’ for example.

TODO & Issues

• Add descriptions (doctext) of template engine and library specific options: WIP

• Add descriptions (doctext) how anytemplate wraps each template engine and library: WIP

• Complete unit tests:

  • Add test cases of each template engine specific options: WIP

• Stablize public and private (internal) APIs:

  • Private APIs still needs a lot of work especially. It’s very vague how it should be as each template engine have its own concept and design and I’m not sure how to abstract them yet.

  • I don’t think public APIs have large issues but these be affected by changes of private APIs more or less; I’m thinking to deprecate the keyword parameter ‘at_cls_args’ for example.

Misc

Alternatives

There are a few libraries works like this:

• TemplateAlchemy: https://pypi.python.org/pypi/TemplateAlchemy/

• collective.templateengines: https://pypi.python.org/pypi/collective.templateengines

These look more feature-rich and comprehensive, but I prefer a lot more lightweight and thin wrapper library along with CLI tool (template renderer) so that I made anytemplate.

And:

• python-jinja2-cli: https://github.com/ssato/python-jinja2-cli

Anytemplate is a successor of python-jinja2-cli.