scan a Python file for Ruby-like string replacements and replace them with Python-like replacements

gistfile1.py

import re, sys, tokenize

RE = re.compile(r'#\{([^}]+)\}')

def transform(s):
    args = []
    def sub(m): args.append(m.group(1)); return "%s"
    s = RE.sub(sub, s)
    return "(%s %% (%s,))" % (s, ", ".join(args)) if args else s

def tokenizer(readline):
    for t in tokenize.generate_tokens(readline):
        if t[0] == 3:
            yield t[0], transform(t[1]), t[2], t[3], ""
        else:
            yield t

with open(__file__) as f:
    print tokenize.untokenize(tokenizer(f.readline))