I don’t know much Ruby, and probably won’t learn; all that syntax and magic scare me away. But I have to admit it has some darned useful gadgets. Here’s a python function I hacked up to do something much like Ruby’s expression-substitution, using the same #{ } syntax. It doesn’t allow curly braces inside the #{ }; were I a little less lazy I would put in some escaping.
import re
import sys
def esub(s):
"""
Perform Ruby-like expression substitution.
>>> x=3
>>> y='A'
>>> esub('abc#{x}def#{3+5}hij#{"".join([y, y])}')
'abc3def8hijAA'
"""
restr = r'(?:#{(?P[^{}]*)})|(?:[^#])+|#'
fr = sys._getframe(1)
def process(m):
txt = m.group('exp')
if txt is not None:
val = eval(txt, fr.f_globals, fr.f_locals)
return type(s)(val)
else:
return m.group()
return ''.join(process(m) for m in re.finditer(restr, s))
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Tags: Programming, python, ruby
March 1, 2008 at 10:10 am |
What’s about this:
def m(a):
def n():
return esub(‘#{a}’)
return n()
m(42)
your approach cannot deal with free variables in inner functions, unfortunately.
March 1, 2008 at 12:38 pm |
D’oh! Oh well.
A not-great workaround:
def m(a):
def n():
a
return esub(’#{a}’)
return n()
m(42)