Generate random id (please help!)

[fracjackmac]

Hi All!

I need to write a function that returns a random id for an employee. Can anybody tell me why it returns... "None"? I'm stuck with it...

import random
import string

def generate_id(number_of_small_letters=4,
                number_of_capital_letters=2,
                number_of_digits=2,
                number_of_special_chars=2,
                allowed_special_chars=r"_+-!"):
    
    small_letters = string.ascii_lowercase
    capital_letters = string.ascii_uppercase
    digits = "0123456789"
    
    
    result_small = ''.join(random.choice(small_letters) for i in range (number_of_small_letters))
    result_capital = ''.join(random.choice(capital_letters) for i in range (number_of_capital_letters))
    result_digits = ''.join(random.choice(digits) for i in range (number_of_digits))
    result_special_characters = ''.join(random.choice(allowed_special_chars) for i in range (number_of_special_chars))
    
    random_characters = result_digits + result_small + result_capital + result_special_characters
    
    random_characters_list = list(random_characters.strip(" "))
   
    final_result = random.shuffle(random_characters_list)
    
    return str(final_result)
    

Taking a step back and breaking the problem into smaller pieces is always a good idea when you bump up against something that doesn't work the way you expect it to.

Here's one approach that leverages the Python interactive interpreter:

>>> import random
>>> import string
>>>
>>> number_of_small_letters=4
>>> small_letters = string.ascii_lowercase
>>>
>>> result_small = ''.join(random.choice(small_letters) for i in range (number_of_small_letters))
>>> result_small
'tjso'
>>>
>>> random_characters = result_small
>>> random_characters_list = list(random_characters.strip(" "))
>>> random_characters_list
['t', 'j', 's', 'o']
>>>
>>> r = random.shuffle(random_characters_list)
>>> r
>>> 
>>> repr(r)
'None'
>>>
>>> random_characters_list
['s', 'o', 'j', 't']
>>> 
>>> help(random.shuffle)
Help on method shuffle in module random:

shuffle(x, random=None) method of random.Random instance
    Shuffle list x in place, and return None.

    Optional argument random is a 0-argument function returning a
    random float in [0.0, 1.0); if it is the default None, the
    standard random.random will be used.

---

Per the output of help(), the shuffle method worked exactly as advertised.

Shuffle list x in place, and return None.


Hopefully, the investigative work above would have pointed you towards the solution called out by @Gribouillis and @deanhystad :

return "".join(random_characters_list)