Python regular expression confusion

Question

Why is it that when I run the following in the python interpreter

re.findall(r'^-?[0-9]+$', "[50, 4]")

I get [] as the result? If I'm not mistaken this should return [50, 4].

What about this ast.literal_eval("[50, 4]") ?

Avinash Raj
– Avinash Raj

2015-04-04 05:14:42 +00:00
Commented Apr 4, 2015 at 5:14 — Avinash Raj
– Avinash Raj, Commented Apr 4, 2015 at 5:14

thefourtheye · Accepted Answer · 2015-04-04 05:11:35Z

2

You are using ^...$. They mean the beginning and the ending of the string. So, you are actually trying to find out if the entire string (from the starting till the ending) is full of numbers. Just drop them and you will get what you wanted

>>> re.findall(r'-?[0-9]+', "[50, 4, -123]")
['50', '4', '-123']

If you want to convert all of them to actual numbers, then apply int function with a list comprehension, like this

>>> [int(num) for num in re.findall(r'-?[0-9]+', "[50, 4, -123]")]
[50, 4, -123]

answered Apr 4, 2015 at 5:11

thefourtheye

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1 Comment

Danny Over a year ago

thefourtheye hit the nail on the head. That's why I'm using regular expressions over literaleval.

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