On Jan 18, 10:21 am, superpollo <ute...@esempio.net> wrote:
> superpollo ha scritto:
>
> > hi.
>
> > what is the most pythonic way to substitute substrings?
>
> > eg: i want to apply:
>
> > foo --> bar
> > baz --> quux
> > quuux --> foo
>
> > so that:
>
> > fooxxxbazyyyquuux --> barxxxquuxyyyfoo
>
> > bye
>
> i explain better:
>
> say the subs are:
>
> quuux --> foo
> foo --> bar
> baz --> quux
>
> then i cannot apply the subs in sequence (say, .replace() in a loop),
> otherwise:
>
> fooxxxbazyyyquuux --> fooxxxbazyyyfoo --> barxxxbazyyybar -->
> barxxxquuxyyybar
>
> not as intended...
Not sure if it's the most pythonic, but I'd probably do it like this:
def token_replace(string, subs):
subs = dict(subs)
tokens = {}
for i, sub in enumerate(subs):
tokens[sub] = i
tokens[i] = sub
current = [string]
for sub in subs:
new = []
for piece in current:
if type(piece) == str:
chunks = piece.split(sub)
new.append(chunks[0])
for chunk in chunks[1:]:
new.append(tokens[sub])
new.append(chunk)
else:
new.append(piece)
current = new
output = []
for piece in current:
if type(piece) == str:
output.append(piece)
else:
output.append(subs[tokens[piece]])
return ''.join(output)
>>> token_replace("fooxxxbazyyyquuux", [("quuux", "foo"), ("foo", "bar"),
>>> ("baz", "quux")])
'barxxxquuxyyyfoo'
I'm sure someone could whittle that down to a handful of list comps...
Iain
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