Python分裂不是预期的结果

Question

I'm trying to cut a string into pieces in Python with the following code:

re.split("[AZ][az]?[0-9]*","CO2")

I expect some result like this:

["C","O2"]

however I get:

['','','']

Answer 1

Since you have no capturing groups in your re, the things you split on are not part of the result. What you're getting is the empty string before the 'C', the empty string between 'C' and 'O2' and the empty string after 'O2'.

If you use

re.split("([A-Z][a-z]?[0-9]*)","CO2")

you'll get

['', 'C', '', 'O2', '']

One dirty approach would be to use

filter(None, re.split("([A-Z][a-z]?[0-9]*)","CO2"))

to remove elements that are not truthy (in this case, empty strings).

Answer 2

If you want to split

Use look arounds like this:

(?<=[A-Z\d])(?=[A-Z])

Regex live here.

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Else

To simply match (without split):

[A-Z][a-z]?\d*

Regex live here.

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Hope it helps.

Answer 3

You can also use this one:

>>> import re
>>> x = re.findall(r"^([A-Z][a-z]?)([A-Z][0-9]*)$","CO2")
>>> list(x[0])
['C', 'O2']