How i can use filter function in python?

Question

I want to delete unwanted characters in dictionary like:$&@“”’’!?,#%*=…
I just want number ,alphabet and underline.

Answer 1

you could do a lambda that returns True if the text isn't in punctuation symbols (that you don't want), except for '_' that we will remove with .replace("_",""), and then using the filter function to apply that to a list, then to join with '':

from string import punctuation
string_to_parse = "a$ ehl! th!s i$ "
parse=lambda letter:letter not in punctuation.replace("_",'') 
stringcompleted = ''.join(filter(parse,string_to_parse))
print(stringcompleted)

output:

'a ehl ths i '

You could wrap this into a function, like this:

>>> def parses(string_to_parse):
...     parse=lambda letter:letter not in __import__("string").punctuation.replace("_",'')
...     return ''.join(filter(parse,string_to_parse))
...
>>> parses("s/)+(=i;~q8cze%]*'y:|,f")
'siq8czeyf'

but this uses dynamic importing, witch from my test, results in double the time of the other so i suggest normal importing:

>>> def parses(string_to_parse):
...    from string import punctuation
...    parse=lambda letter:letter not in punctuation.replace("_",'')
...    return ''.join(filter(parse,string_to_parse))
>>> parses("s/)+(=i;~q8cze%]*'y:|,f")
'siq8czeyf'

Answer 2

If you want to sanitize a string so that it has all special characters removed, try this function:

def sanitize(string):
  outstr = ""
  for char in string:
    if char.isalpha() or char.isdigit() or char == "_":
      outstr += char
  return outstr