Fast way to split alpha and numeric chars in a python string

Question

I am trying to work out a simple function to capture typos, e.g:

"Westminister15"
"Westminister15London"
"23Westminister15London"

after fixating:

["Westminister", "15"]
["Westminister", "15", "London"]
["23", "Westminister", "15", "London"]

First attempt:

 def fixate(query):
     digit_pattern = re.compile(r'D')
     alpha_pattern = re.compile(r'd')
     digits = filter(None, digit_pattern.split(query))
     alphas = filter(None, alpha_pattern.split(query))
     print digits
     print alphas

result:

 fixate("Westminister15London")

 > ['15']
 > ['Westminister', 'London']

However, I think this could be done more effectively, and I still get bad results when I try something like:

 fixate("Westminister15London England")

 > ['15']
 > ['Westminister', 'London England']

Obviously it should enlist London and England separately, but I feel my function will get overly patched and theres a simpler approach

This question is somewhat equivalent to this php question

Asked By: Hedde van der Heide

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Source

Answer 1

You can get the desired result with re.findall():

>>> re.findall(r"[^Wd_]+|d+", "23Westminister15London")
['23', 'Westminister', '15', 'London']
>>> re.findall(r"[^Wd_]+|d+", "Westminister15London England")
['Westminister', '15', 'London', 'England']

d+ matches any number of digits, [^Wd_]+ matches any word.

re.split() would also be possible in current Python versions since splits on zero-length matches are now supported, but the resulting regex is much more complicated, so I still recommend the old approach.

Answered By: Tim Pietzcker

Answer 2

You can use this regex instead of yours:

>>> import re
>>> regex = re.compile(r'(d+|s+)')
>>> regex.split('Westminister15')
['Westminister', '15', '']
>>> regex.split('Westminister15London England')
['Westminister', '15', 'London', ' ', 'England']
>>>

Then you have to filter the list removing empty strings/white-space only strings.

Answered By: Bakuriu

Answer 3

Here’s another approach in case you prefer to stay away from regex, which sometimes can be unwieldy if one is not familiar enough to make it/change it themselves:

from itertools import groupby

def split_text(s):
    for k, g in groupby(s, str.isalpha):
        yield ''.join(g)

print(list(split_text("Westminister15")))
print(list(split_text("Westminister15London")))
print(list(split_text("23Westminister15London")))
print(list(split_text("Westminister15London England")))

returns:

['Westminister', '15']
['Westminister', '15', 'London']
['23', 'Westminister', '15', 'London']
['Westminister', '15', 'London', ' ', 'England']

The generator can be easily modified, too, to never yield whitespace strings if desired.

Answered By: hexparrot

Fast way to split alpha and numeric chars in a python string

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