Regex [] vs () in Python with respect to re.split()

Question

What is the difference between [,.] and (,|.) when used as a pattern in re.split(pattern,string)? Can some please explain with respect to this example in Python:

import re
regex_pattern1 = r"[,\.]"
regex_pattern2 = r"(,|\.)"
print(re.split(regex_pattern1, '100,000.00')) #['100', '000', '00']
print(re.split(regex_pattern2, '100,000.00'))) #['100', ',', '000', '.', '00']

Answer 1

[,\.] is equivalent to ,|\..^[1]

(,|\.) is equivalent to ([,\.]).

() creates a capture, and re.split returns captured text as well as the text separated by the pattern.

>>> import re
>>> re.split(r'([,\.])', '100,000.00')
['100', ',', '000', '.', '00']
>>> re.split(r'(,|\.)', '100,000.00')
['100', ',', '000', '.', '00']
>>> re.split(r',|\.', '100,000.00')
['100', '000', '00']
>>> re.split(r'(?:,|\.)', '100,000.00')
['100', '000', '00']
>>> re.split(r'[,\.]', '100,000.00')
['100', '000', '00']

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1. You might sometime need (?:,|\.) to limit what is considered the operands of | when you embed it in a larger pattern, though.