Elegant way to extract values from a string parsed with a template

Question

Hello all,

I have a template like this:

foo_tmplte = Template("fieldname_${ln}_${type} = $value")

and a lot of strings parsed with this template like this:

foo_str1 = "fieldname_ru_ln = journal"
foo_str2 = "fieldname_zh_TW_ln = journal"
foo_str3 = "fieldname_uk_ln = номер запису"

Now i want to extract back the variables from the template, for example with str1 the result must be:

ln = ru
type = ln
value = journal

I try some approaches but I can't find any elegant and reusable function to extract the variables. Any idea?

Thanks in advance

Answer 1

Why don't you use regexps? They have named groups and you can extract them in a dictionary.

Tue Aug 17 14:33:58 $ python
Python 2.6.5 (r265:79063, Jun 12 2010, 17:07:01) 
[GCC 4.3.4 20090804 (release) 1] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import re 
>>> foo_template = re.compile(r"^fieldname_(?P<ln>\w+?)_(?P<type>\w+) = (?P<value>.*)$")
>>> m = foo_template.match("fieldname_zh_TW_ln = journal")
>>> m
<_sre.SRE_Match object at 0x7ff34840>
>>> m.groupdict()
{'ln': 'zh', 'type': 'TW_ln', 'value': 'journal'}
>>> 

Answer 2

You could use Jinja2, a general-purpose templating library. You'd have to change the string format, though:

"fieldname_{{ ln }}"