Extremely simple Python Templating Engine

template.py

"""
# template.py

Extremely simple Python Templating Engine

This is a no-frills templating engine written in Python. I chose to
write this when I decided that I wanted something that was extremely
simple templating system and even str.format seemed like overkill.

You can use either a string as a template, or a file. NOTE, however,
that the file will be read entirely into memory, so if working with
large files you should either iterate through it yourself or use a more
fully-featured templating engine (I would probably recomend Jinja2).

to use a string as a template use render_template, and to use a file
use render_template_file.
"""

def render_template(string, mapping):
    """
    ## render_template
    
    given string and mapping where string is a Python string
    and mapping is a hasable object (such as a dict), any
    occurances of <%key_name%> will be replaced with the
    value associated with key_name within mapping. for
    example:
    
    >>> m = {"name": "ilovetux", "sex": "male"}
    >>> s = "Hello, my name is <%name%> and I am <%sex%>."
    >>> print render_template(s, m)
    Hello, my name is ilovetux and I am male.
    """
    for k, v in mapping.items():
        string = string.replace("<%{}%>".format(k), v)
    return string


def render_template_file(fname, mapping):
    """
    render_template_file
    
    NOTE: file fname will be read entirely into memory, so you
    probably shouldn't use this on large files.
    
    given fname and mapping where fname is a string containing
    a filename and mapping is a hasable object (such as a dict),
    any occurances of <%key_name%> will be replaced with the
    value associated with key_name within mapping. for
    example:
    
    in file /tmp/text.html
    
    ```
    <h1>hello, my name is <%name%></h1>
    <h2>I am <%sex%></h2>
    ```
    
    >>> m = {"name": "ilovetux", "sex": "male"}
    >>> print render_template_file("/tmp/text.html")
    <h1>hello, my name is ilovetux</h1>
    <h2>I am male</h2>
    """
    with open(fname, "r") as fin:
        ret = render_template(fin.read(), mapping)
    return ret