How to do CamelCase split in python
Working solution, without regexp
I am not that good at regexp. I like to use them for search/replace in my IDE but I try to avoid them in programs.
Here is a quite straightforward solution in pure python:
def camel_case_split(s):
idx = list(map(str.isupper, s))
# mark change of case
l = [0]
for (i, (x, y)) in enumerate(zip(idx, idx[1:])):
if x and not y: # "Ul"
l.append(i)
elif not x and y: # "lU"
l.append(i+1)
l.append(len(s))
# for "lUl", index of "U" will pop twice, have to filter that
return [s[x:y] for x, y in zip(l, l[1:]) if x < y]
And some tests
def test():
TESTS = [
("aCamelCaseWordT", ['a', 'Camel', 'Case', 'Word', 'T']),
("CamelCaseWordT", ['Camel', 'Case', 'Word', 'T']),
("CamelCaseWordTa", ['Camel', 'Case', 'Word', 'Ta']),
("aCamelCaseWordTa", ['a', 'Camel', 'Case', 'Word', 'Ta']),
("Ta", ['Ta']),
("aT", ['a', 'T']),
("a", ['a']),
("T", ['T']),
("", []),
("XYZCamelCase", ['XYZ', 'Camel', 'Case']),
("CamelCaseXYZ", ['Camel', 'Case', 'XYZ']),
("CamelCaseXYZa", ['Camel', 'Case', 'XY', 'Za']),
]
for (q,a) in TESTS:
assert camel_case_split(q) == a
if __name__ == "__main__":
test()
Use re.sub()
and split()
import re
name = 'CamelCaseTest123'
splitted = re.sub('([A-Z][a-z]+)', r' \1', re.sub('([A-Z]+)', r' \1', name)).split()
Result
'CamelCaseTest123' -> ['Camel', 'Case', 'Test123']
'CamelCaseXYZ' -> ['Camel', 'Case', 'XYZ']
'XYZCamelCase' -> ['XYZ', 'Camel', 'Case']
'XYZ' -> ['XYZ']
'IPAddress' -> ['IP', 'Address']
Most of the time when you don't need to check the format of a string, a global research is more simple than a split (for the same result):
re.findall(r'[A-Z](?:[a-z]+|[A-Z]*(?=[A-Z]|$))', 'CamelCaseXYZ')
returns
['Camel', 'Case', 'XYZ']
To deal with dromedary too, you can use:
re.findall(r'[A-Z]?[a-z]+|[A-Z]+(?=[A-Z]|$)', 'camelCaseXYZ')
Note: (?=[A-Z]|$)
can be shorten using a double negation (a negative lookahead with a negated character class): (?![^A-Z])
As @AplusKminus has explained, re.split()
never splits on an empty pattern match. Therefore, instead of splitting, you should try finding the components you are interested in.
Here is a solution using re.finditer()
that emulates splitting:
def camel_case_split(identifier):
matches = finditer('.+?(?:(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])|$)', identifier)
return [m.group(0) for m in matches]