Remove non-numeric characters from a Python string

Question

Let’s say, I have:

a = "0LÁM@UN@D0

I would like something to remove all letters (A-Z) and other characters, I just want to get the numbers, in the example, would be only 0 and 0

b = "A1B2C3"

Something that takes letters from alphabets and characters, that deletes anything other than numbers (integers) in one string.

I’m using Python 2.7

Answer 1

You can use regex to solve your problem:

import re
b = "A1B2C3"
b = re.sub('[^0-9]', '', b)

# 123
print(b)

Explanation

The function sub(), first receives a pattern in the first parameter, a new string which will be used to replace when you find this pattern in string in the second parameter, and in the last parameter a string that you want to look for the pattern.

Regex

In the first parameter we are passing a regex to remove everything that is not number from the string, a brief explanation about it:

[0-9]: will pick up all digits from 0 to 9

[^0-9] : will take everything that is not digit

Answer 2

An alternative to Marcelo’s answer is to make a Join only of the digit:

>>> a = "0LÁM@UN@D0"
>>> b = "A1B2C3"
>>> ''.join(c for c in a if c.isdigit())
'00'
>>> ''.join(c for c in b if c.isdigit())
'123'
>>> 

Answer 3

Another possible way to resolve this issue is by using the function filter associated with lambda. This way the code would be:

s = input('Digite uma string: ')
resultado = ''.join(filter(lambda i: i if i.isdigit() else None, s))

print(resultado)

Testing the code:

By executing said code and typing...

A1B2C3

...and press Enter, we will receive as an exit:

123