Python template engine

Question

Could it be possible if somebody could help me get started in writing a python template engine? I\'m new to python and as I learn the language I\'ve managed to write a littl

Answer 1

Well, when I decide to play around like you did, TDD is always a good way to go.

so, why not give it a go?

for example, create a file called jturo_template.py and write:

import re
import unittest

class JTuroTemplate(object):
    u"""JTuro's template engine core class"""
    variable_regex = r'\$\{((.*)(%s)([^}]*))*\}'
    def __init__(self, string):
        self.string = string

    def __repr__(self):
        pieces = self.string.split()
        if len(pieces) > 3:
            head = "%s ..." % " ".join(pieces[:3])
        else:
            head = " ".join(pieces)

        return u'' % (head)

    def render(self, context):
        new = unicode(self.string)

        for key, value in context.items():
            variable_name = re.escape(key)
            regex = re.compile(self.variable_regex % variable_name)

            for match in regex.findall(new):
                if match[0]:
                    replacement = match[0].replace(key, repr(value))
                    new = new.replace('${%s}' % match[0], unicode(eval(replacement)))

        return new

class TestJTuroTemplate(unittest.TestCase):
    def test_repr(self):
        "a instance will be nicely represented"
        jt = JTuroTemplate('my template')
        self.assertEquals(repr(jt), '')

    def test_repr_truncated(self):
        "the python representation is truncated after 3 words"

        jt = JTuroTemplate('such a long string template')
        self.assertEquals(repr(jt), '')

    def test_solves_simple_variables(self):
        "it solves simple variables"

        jt = JTuroTemplate('my variable is ${var} == 4')
        self.assertEquals(jt.render({'var': '4'}), 'my variable is 4 == 4')

    def test_solves_variables_with_python_code(self):
        "it solves variables with python code"

        jt = JTuroTemplate('my variable is ${var + var} == 44')
        self.assertEquals(jt.render({'var': '4'}), 'my variable is 44 == 44')

if __name__ == '__main__':
    unittest.main()

Sorry for the long post, but I think you can try this workflow:

1. write test that fail
2. run and watch it fail
3. write code to make the test pass
4. run again and watch it pass