how to remove non-alphanumeric characters except \ / @ + -:, | #

Question

I have

import re

cadena = re.sub('[^0-9a-zA-Z]+', '', cadena)

how to remove non-alphanumeric characters except this \ / @ + -:, | #

Answer 1

Make sure to escape the backslash inside the character class. Use raw string for regular expression, it eliminates need in further escaping.

cadena = re.sub(r'[^0-9a-zA-Z\\/@+\-:,|#]+', '', cadena)

Please note that the underscore is considered an alphanumeric character. If you don't need to strip it, you can simplify the expression.

cadena = re.sub(r'[^\w\\/@+\-:,|#]+', '', cadena)

Answer 2

Example 1: (Most easy way I think)

# String
string = 'ABC#790@'
# Remove the #, @ and 7 from the string. (You can choose whatever you want to take out.)
line = re.sub('[#@7]', '', string)
# Print output
print(line)

Example 2:

You can also make use of substrings, that way you can look on every position if a letter matches the letter you don't want in your string. If the letter is one you would like to keep, you add that letter to a new string. Else you pass.

For example: String 's' is your string, and string 'd' conatain letters you want to filter out.

s = 'abc/geG#gDvs@h81'
d = '#@/'
e = ''
i = 0
j = 0
l = len(s)
g = len(d)
a = False

while i < l:
    # Grab a single letter
    letter1 = s[i:i+1]
    # Add +1
    i = i + 1
    # Look if the letter is in string d
    while j < g:
        # Grab a single letter
        letter2 = d[j:j+1]
        # Add +1
        j = j + 1
        # Look if letter is not the same.
        if (letter1 != letter2):
            a = True
        else: 
            a = False
            break
    # Reset j
    j = 0
    # Look if a is True of False. 
    # True: Letter does not contain letters from string d. 
    # False: Letter does contain letters from string d.
    if (a == True):
        e = e + letter1
    else: 
        pass

# Print the result
print(e)