Split string based on regex pattern

Question

I have a message which I am trying to split.

import re

message = "Aug 10, 17:04 UTCThis is update 1.Aug 10, 15:56 UTCThis is update 2.Aug 10, 15:55 UTCThis is update 3."

split_message = re.split(r'[a-zA-Z]{3} (0[1-9]|[1-2][0-9]|3[0-1]), ([0-1]?[0-9]|2[0-3]):[0-5][0-9] UTC', message)

print(split_message)

Expected Output:

["This is update 1", "This is update 2", "This is update 3"]

Actual Output:

['', '10', '17', "This is update 1", '10', '15',  "This is update 2", '10', '15', "This is update 3"]

Not sure what I am missing.

Aram Becker · Accepted Answer · 2021-08-25 15:48:54Z

4

You are using "capturing groups", this is why their content is also part of the result array. You'll want to use non capturing groups (beginning with ?:):

import re

message = "Aug 10, 17:04 UTCThis is update 1.Aug 10, 15:56 UTCThis is update 2.Aug 10, 15:55 UTCThis is update 3."

split_message = re.split(r"[a-zA-Z]{3} (?:0[1-9]|[1-2][0-9]|3[0-1]), (?:[0-1]?[0-9]|2[0-3]):[0-5][0-9] UTC", message)

print(split_message)

You will however always get an empty entry first, because an empty string is in front of your first split pattern:

['', 'This is update 1.', 'This is update 2.', 'This is update 3.']

As statet in the docs:

If capturing parentheses are used in pattern, then the text of all groups in the pattern are also returned as part of the resulting list.

edited Aug 25, 2021 at 15:48

answered Aug 25, 2021 at 15:42

Aram Becker

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1 Comment

Wiktor Stribiżew Over a year ago

print([x for x in split_message if x]) will remove the empty elements.

Jeremy Savage · Accepted Answer · 2021-08-25 15:32:50Z

0

Not using regex, but wanted to highlight the power of Python string splitting for tasks like this. Way less headaches as easier to understand.

message = "Aug 10, 17:04 UTCThis is update 1.Aug 10, 15:56 UTCThis is update 2.Aug 10, 15:55 UTCThis is update 3."
values = message.split("UTC")
values = values[1:]
result = [v.split(".")[0] for v in values]

Note: this may not work if your messages ("This is update 1.") contain multiple . symbols.

answered Aug 25, 2021 at 15:32

Jeremy Savage

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2 Comments

PritamYaduvanshi Over a year ago

Thanks for reply. It won't work for my use-case. As you mentioned my message may have multiple "." or none at all or it can also have 'UTC' in it. Only thing I am certain is that it will have date pattern like(Aug 10, 17:04 UTC) and that's why going after regex for solution.

Jeremy Savage Over a year ago

Ah yes, the value of context. Looks like Aram Becker has given a good answer. Will leave this answer here in case anyone finds it valuable in the future.

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