在Python中的字符串中搜索数字

Question

I have a list of strings that contain letters and numbers. I want to search for the numbers and have them returned to me. What is the best way to do this? I'm pretty new to Python and I looked into regular expressions and I'm in the process of learning them now, but I don't know when I'll be good enough in regular expressions before I can use them.

Answer 1

To return all numbers in all strings in a list named inputlist , you can use a list comprehension:

import re

numbers = [int(num) for value in inputlist for num in re.findall('\d+', value)]

This casts the numbers to integers as well. If you needed floating point values (so, numbers with a decimal point in them), add on a pattern for one decimal point flanked by digits:

numbers = [float(num) for value in inputlist for num in re.findall('\d+(?:\.\d*)', value)]

If, however, you are only looking for strings that are numbers (rather than just contain numbers), str.isdigit() may suffice:

numbers = [int(value) for value in inputlist if value.isdigit()]

Note that this will not match floating point numbers ( str.isdigit() is only True if all characters are digits; a decimal point doesn't count).

Answer 2

You can use isdigit :

numbers = [n for n in strings if n.isdigit()]

If you actually want to parse them:

numbers = [int(n) for n in strings if n.isdigit()]

This is assuming that you only want the strings that are all digits, and you will want to ignore strings that are mixed letters and numbers. Unfortunately, it's unclear from your question which you actually want. You also didn't specify whether or not the numbers represent integers, or they might representing floating-point values. :-(