extract variables from python string template

Question

For python string template is there a clean way to extract the variable names in the template string.

I actually want to to be able to write template stings into a textfield on and then substitue the variables for other more complex looking variables.

So for example I would get user inputted template into a variable

t = Template(( request.POST['comment'] ))

the comment string maybe

'$who likes $what'

I need an array of the variables names so I can convert the string to something like

{{{who}}} likes {{{what}}}

Maybe there is also a better way to approach this.

andrew cooke · Accepted Answer · 2012-04-15 01:26:03Z

3

i don't know of any template-related api, but you can use a regexp:

>>> import re
>>> rx = re.compile(r'\$(\w+)')
>>> rx.sub(r'{{{\1}}}', '$who likes $what')
'{{{who}}} likes {{{what}}}'

the first argument to rx.sub() replaces each occurrence of a variable in the second argument, with \1 being replaced by the name of the variable.

edited Apr 15, 2012 at 1:26

answered Apr 15, 2012 at 1:09

andrew cooke

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Joel Cornett · Accepted Answer · 2012-04-15 01:08:37Z

1

def replaceVars(matchObj):
    return "{{{%s}}}" % matchObj.groups()[0]

c = r"\$(\w+)\s*"

s = "$who likes $what"

converted = re.sub(c, replaceVars, s)

answered Apr 15, 2012 at 1:08

Joel Cornett

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3 Comments

evolution Over a year ago

This seems to be the best way right now. I am however struggling as I need to print the variable twice. It is more like {{{%s|something%s}}}

Joel Cornett Over a year ago

Like {{{who|somethingwho}}}, for example? Then just modify the replaceVars function.

evolution Over a year ago

cool - got it - just neede % ( matchObj.groups()[0], matchObj.groups()[0])

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