Python Regex - Create explicit multiplication -


i want replace implicit multiplication in strings (such "ax") explicit multiplication (such "ax"). have of done, except wanted add replace such "a(x+1)" "a(x+1)".

so far, pattern is:

pattern = re.compile("([0-9]+|[a-z\)])([a-z\(])", re.ignorecase)

i using pattern.sub actual replacing:

s = "rx(3x)r" print pattern.sub('\\1*\\2', s)

however, not replace "a(" "a*(". how can fix this?

you can use lookahead assertion:

>>> pattern = re.compile("([0-9]+|[a-z\)])(?=[a-z\(])", re.ignorecase) >>> s = "rx(3x)r" >>> print pattern.sub('\\1*', s) r*x*(3*x)*r

the problem regex pattern matches rx , inserts *. however, can't match x again insert * between x(. if use lookahead, don't consume x available matched part of expression. of course, here sub pattern needs change since there no second group.


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