ptemplate — lightweight, data-driven templating

ptemplate is a lightweight templating engine for Python, heavily inspired by Google’s ctemplate language. Like ctemplate, ptemplate strongly separates the application’s logic and presentation. At its heart, ptemplate is an extension of Python’s advanced string formatting facility – it extends the interpreter’s built-in formatters to provide a fast, expressive, content-agnostic templating system.

Installing ptemplate

You can install the latest stable version of ptemplate using pip:

$ pip install ptemplate

Mirrors of the project’s repository are hosted at and – feel free to clone and issue pull requests at either service. For git users:

$ git clone

And for Mercurial users:

$ hg clone

Both github and bitbucket provide feeds of changes to the project; for example:

If you’d like to contribute an improvement to ptemplate, please consider using either of the above services. Otherwise, send an email to

A quick tour of ptemplate‘s features

Simple extension of Python’s advanced string formatting API (PEP 3101):

>>> from ptemplate.formatter import Formatter
>>> formatter = Formatter()
>>> template = """normal variable substitution: {var}"""
>>> formatter.format(template, var="foo")
'normal variable substitution: foo'

>>> template = """{#section}this is {something} {/section}"""
>>> data = {"section": [{"something": "fast"}, {"something": "easy"}, {"something": "simple"}]}
>>> formatter.format(template, **data)
'this is fast this is easy this is simple '

>>> template = """{%this is a comment}"""
>>> formatter.format(template, **{})

Content filtering system (eg HTML sanitization):

>>> import cgi
>>> from ptemplate.template import Template
>>> templater = Template()
>>> templater.converters["h"] = cgi.escape

>>> data = {"content": """<p>some HTML from the wild</p>"""}
>>> templater.template = """something dangerous: {content!h}"""
>>> templater.render(data)
'something dangerous: &lt;p&gt;some HTML from the wild&lt;/p&gt;'

>>> data = {"section": [{"example": "<p>paragraph</p>"},{"example": "no html here"}]}
>>> templater.template = """you can sanitize entire sections, too ({#section!h}{example} {/section})"""
>>> templater.render(data)
'you can sanitize entire sections, too (&lt;p&gt;paragraph&lt;/p&gt; no html here )'

Basic compatibility with Google’s ctemplate:

>>> from ptemplate.ctemplate import CTemplate
>>> template = """Google is {{#section}}{{something}}, {{/section}}"""
>>> templater = CTemplate(template=template)
>>> data = {"section": [{"something": "not evil"},{"something": "a company"}]}
>>> templater.render(data)
'Google is not evil, a company, '

Basic usage

Despite its simple syntax, templates processed by ptemplate can still produce very complex documents. Unlike most template systems, ptemplate encourages you to keep application logic where it belongs – in your application. Expansion of the template is controlled solely by the structure of your data. This keeps the templating engine itself simple and fast and makes writing and debugging your templates even easier. For more on the philosophy behind data-driven templating systems, see “How To Use the Google Template System”.

All of the ptemplate interfaces take a single data dictionary and use it to expand a simple string template. The data dictionary’s keys are plain strings; its values are either strings or lists of other data dictionaries. Other objects may be used as values, but they will be converted to strings before being inserted into the template. String values are substituted for variables in the template. List values control the number of iterations (and scope) of section variables.

Templates are composed of plain text with (optional) variable and section markers. ptemplate markers must all be valid field names as described in PEP 3101 and begin and end with ‘{‘ and ‘}’, respectively. Special fields denoting comments and the beginning and end of sections are marked with a single-character indicator (‘!’, ‘#’, ‘/’). Comment fields are ignored completely. Sections are expanded once for each data dictionary found in the evaluation scope.

Variable expansion proceeds from the innermost context to the outermost; if no match is found, an empty string is substituted instead. Variables defined within a section will first attempt to match keys in that section’s dictionary. If no match is found, the dictionary in which the section is defined will be searched for a match. This process continues until all dictionaries (or “scopes”) are exhausted.

For example, this deeply nested data dictionary produces the following:

>>> from ptemplate.template import Template
>>> templater = Template()

>>> data = {
...     "outer": [
...         {"foo": "foo",
...         "middle": [
...             {"foo": "bar",
...             "inner": [
...                 {"foo": "baz"},
...             ]},
...         ]},
...     ]}
>>> template = """{#outer}outer: {foo} {#middle}middle: {foo} {#inner}inner: {foo} {/inner}{/middle}{/outer}"""
>>> templater.template = template
>>> templater.render(data)
'outer: foo middle: bar inner: baz '

At each level, a new value for “foo” is defined. If the innermost value is removed, though, the next-highest value is used:

>>> data["outer"][0]["middle"][0]["inner"][0].pop("foo")
>>> templater.render(data)
'outer: foo middle: bar inner: bar '

ctemplate support

Since ptemplate and Google’s ctemplate are so similar internally, it’s fairly easy to process ctemplate templates with ptemplate. In fact, with a very naive preprocessor, ptemplate.ctemplate can pass many of Google’s ctemplate unittests. To expand ctemplate(-like) templates, use ptemplate.ctemplate.CTemplate instead of ptemplate.template.Template.


ptemplate.ctemplate.CTemplate does not provide full ctemplate compatibility. See the class documentation for specific exceptions.


You have access to the templating system at three levels. First, you can interact directly with ptemplate.formatter.Formatter, which offers an interface very similar to Python’s advanced string formatting (string.Formatter, PEP 3101). Second, you can work with (or subclass) ptemplate.template.Template, a thin wrapper around the formatter that also adds a Buffet-style API. Lastly, you can use ptemplate.ctemplate.CTemplate. CTemplate extends Template with a preprocessor that supports a subset of Google’s ctemplate system. ctemplate also demonstrates how to subclass and extend the basic template.

For a typical use case, ptemplate.template is probably most useful as it provides a familiar API. ptemplate.ctemplate should (with, perhaps, a few changes to the preprocessor) support many simple templates written for Google’s ctemplate system. For smaller projects (or doing things like formatting error messages), ptemplate.formatter may be sufficient on its own.

ptemplate.formatter – extended string formatter

This module extends the advanced string formatter (PEP 3101) available in Python versions greater than 2.5. In addition to regular variable substitution and formatting, Formatter supports sections and in-template comments.

class ptemplate.formatter.Formatter(*args, **kwargs)

Bases: string.Formatter

A string formatter.

Formatter extends the advanced string formatter described in PEP 3101 and implemented in Python versions greater than 2.5. It provides hooks that simplify token conversion (converters) and recognize special template variables (markers). Since it uses str._formatter_parser() (implemented in C in the standard interpreter) to parse the input string, it should also perform relatively well.

convert_field(value, conversion)

Convert a field value according to a conversion specification.

If conversion is registered in converters, the value is passed to the matching converter and the output is returned. Otherwise, the value and conversion specification are passed to string.Formatter.convert_field().


A dictionary of converter functions keyed by conversion strings.

If a token’s conversion string matches a key in this dictionary, convert_field() will use the converter instead of the usual string conversion.


Keys in this dictionary must be one character in length (to match str._formatter_parser()‘s expectations for format flags).

formatsection(tokens, data, scopes=[])

Format a section of a token stream according to data.

formatsection() builds a formatted string from the iterable tokens. If it encounters a section in the stream, it creates a new stream and passes the section (and everything in it) to another invocation of formatsection(), adding its output to the formatted string. This continues recursively until there are no more sections and the stream of tokens is finished. Then, the formatted result is returned.

When a section is completed, its output will be passed to convert_field() and format_field() if the Section.conversion or Section.format attributes were defined, respectively.

get_value(field, args, scopes)

Look up the value of field in scopes.

scopes is a list of data dictionaries associated with each successive parent of the current section. get_value() searches for a key matching field in each of these dictionaries, in order. If no match is found, an empty string is returned. Otherwise, the key’s value (a list of data dictionaries or a string) is returned.


The length of a marker indicator.


A dictionary mapping marker indicators to marker type names.

The extended syntax supported by Formatter is composed of markers within normal template variables. Markers registered here can trigger extended behavior in _vformat().


Tokenize a template string.

tokenize() parses string using string.Formatter.parse() (which in turn relies on str._formatter_parser()) and yields Token instances using the parsed data.

vformat(string, args, kwargs)

Format string according to data in args and kwargs.

Unlike string.Formatter.vformat(), this method does not track (or complain about) unused arguments.

class ptemplate.formatter.Section

A template section.

Constructor arguments should be passed as keywords and include:

name is the name of the section (not including the section marker).

tokens is a list of Token instances that belong in the section.

data is a template data dictionary applicable to the section.

scopes is a list of data dictionaries that should be searched successively when resolving variables in the section.

conversion is a conversion string. If not None, it will be passed with the output of the section to Formatter.convert_field().

format is a format string. If not None, it will be passed with the output of the section to Formatter.format_field().

class ptemplate.formatter.Token

A template token.

Constructor arguments should be passed as keywords and include:

text is the literal text preceding the token.

field is the name of the field (or None), not including the marker indicator.

fieldname is the full name of the field (or None), including the marker indicator.

marker is a marker type registered in Formatter.markers.

spec is a format string passed with the token’s contents to Formatter.format_field().

conversion is a conversion string passed with the token’s contents to Formatter.convert_field().

ptemplate.template – advanced string templating

ptemplate.template provides a Template, a thin interface on top ptemplate.formatter that is more useful for typical templating tasks.

class ptemplate.template.Template(extra_vars_func=None, options=None, template='')

Bases: object

A templater.

Template wraps ptemplate.formatter.Formatter with a Buffet-compatible interface. In addition to the standard Buffet arguments (extra_vars_func, options), the constructor accepts a template string. This string is the template that will be rendered later (by a call to render()).


A dictionary of object converters.

These converters will be passed to the template’s ptemplate.formatter.Formatter instance.


The template’s formatter.

The formatter performs the actual templating work and should have a ptemplate.formatter.Formatter.format() method and a ptemplate.formatter.Formatter.converters dictionary. The converters dictionary will be updated with any converters specified in the Template.


Find a template specified in Python ‘dot’ notation.

Required by Buffet; not supported.


Template preprocessor callable.

This callable should accept the template string as its sole argument. Its output should be another template string. Use this facility to translate foreign template syntaxes into something ptemplate.formatter.Formatter can understand.

render(data, format='html', fragment=False, template=None)

Render the template using data.

The format, fragment and template arguments are ignored. Instead, Template uses template as the template, passing it to preprocessor if necessary. It then expands the template (using formatter) and returns the result as a string.

transform(info, template)

Render the output to Elements.

Required by Buffet; not supported.

ptemplate.ctemplate – ctemplate-like interface

This module implements a templating interface similar Google’s ctemplate with a few important exceptions:

  • templates may not change the field delimiter
  • modifiers are marked with ‘!’
  • comments are marked with ‘%’
  • the templater does not strip whitespace (except by modifiers)
  • includes are not supported
  • pragmas/macros are not supported
  • separator sections are not supported

Like ctemplate, CTemplate expands a string template to match the structure of a dictionary (using ptemplate.template.Template). Data dictionaries may contain either lists of other data dictionaries or single values (string, integer, float, etc). Plain variables are substituted according to the usual Python string formatting rules (see PEP 3101). Sections (fields preceded by ‘#’) are expanded once for each data dictionary contained in the corresponding list.

class ptemplate.ctemplate.CTemplate(*args, **kwargs)

Bases: ptemplate.template.Template

A (somewhat) ctemplate-compatible templater.

Incompatibilities with Google’s ctemplate are documented in ptemplate.ctemplate. Construction of a CTemplate instance is the same as with ptemplate.template.Template.


A global data dictionary.

Template variables that don’t match keys in the main data dictionary may match global keys as a last resort. By default, globals contains BI_NEWLINE and BI_SPACE, which match the newline and space characters, respectively (as in ctemplate).


Convert Google’s ctemplate syntax.

Since ctemplate and ptemplate.template are quite similar internally, a simple translation can make a document (mostly) legible. At the moment, the preprocessor only converts the marker indicators (‘{{‘ and ‘}}’) and comment character (‘!’).

render(data, format='html', fragment=False, template=None)

Render the template.

Here, CTemplate adds the globals dictionary to the data dictionary before calling ptemplate.template.Template.render().

Running the benchmark

The ptemplate repository contains a port of the Genshi benchmark suite. To run the benchmarks:

$ cd tests/bench
$ python | grep -v "not installed" | sort -n -k1.40bn
$ python | grep -v "not installed" | sort -k1.40bn

You can also run benchmarks against selected template engines by passing the engine name (ie “ptemplate”, “ctemplate”) as an argument to the benchmark script.

As of 2010.04.15, the benchmark produced the following results (sorted by ‘’’‘):

Engine Name Version (ms) (ms) Notes
Mako 0.3.2 0.71 190.21  
Genshi_text 0.5.1 2.65 554.41  
Ptemplate 0.1 3.42 1188.61  
Ctemplate 0.1 3.64 1296.58  
Genshi 0.5.1 7.75 1228.97 template
Genshi 0.5.1 n/a 1566.21 tag builder
Django 1.1.1 6.29 1872.76  
Genshi 0.5.1 n/a 1996.71 template + tag builder
Kid 0.9.6 15.34 3508.88  

The test system was:

  • AMD Athlon(tm) 64 Processor 3200+ (“AuthenticAMD” 686-class, 512KB L2 cache)
  • 1 GB RAM
  • OpenBSD 4.7-current
  • Python 2.6.3

See also

There have been several other efforts to bring ctemplate-like templates to Python. For example: