I was building a script to find credit card numbers in files. For PCI compliance reasons.
I wanted to see and or save the credit card numbers in a file but only parts of them, so I still would be compliant.
So I created this small mask_number function to, well... mask found credit card numbers.
To mask a number with * without masking the first 4 and the last 4 numbers in Python using re.sub(), you can use the following regular expression:
import re
def mask_number(number):
return re.sub(r'(?<=\d{4})\d(?=\d{4})', '*', number)
The regular expression works as follows:
(?<=\d{4}): Positive look behind to match any digit that has 4 digits behind it\d: Match any single digit(?=\d{4}): Positive lookahead to match any digit that has 4 digits ahead of it
The re.sub() function will replace all the single digits that match the regular expression with the * character.
Example usage:
>>> mask_number('1234567890123456')
'1234********3456'
>>> mask_number('1234-5678-9012-3456')
'1234-****-****-3456'
In the above example, the function mask_number() takes in a number as a string, and returns a masked string with the first 4 and last 4 digits unmasked and the rest of the digits masked with *.