Using a global variable inside a function

Question

I'm trying to use an already set global variable inside a function, but keep getting an error "Local variable "password" referenced before assigned". Is there something I'm missing to where it can't find the actual global variable?

password = ""
def random_characters(letters):
    add = random.choice(letters)
    password = password + add
letters_strong = string.ascii_letters + string.digits + string.punctuation
for i in range(16):
    random_characters(letters_strong)
print(password)

You need to use the `global` keyword and "import" the globals into the function. — Carcigenicate, Jun 23 '17 at 02:37
@KariFox Lookup how to use the global keyword. Honestly, you should avoid using it when possible, but it's an option if you really need it. — Carcigenicate, Jun 23 '17 at 02:47
This may help: https://stackoverflow.com/questions/423379/using-global-variables-in-a-function-other-than-the-one-that-created-them — Germán Alfaro, Jun 23 '17 at 02:52

score 2 · Answer 1 · answered Jun 23 '17 at 02:38

2

password = password + add

This creates a new local variable which shadows the global variable of the same name. To solve the problem, either use a different name for the local variable or pass a parameter. I strongly suggest the later.

answered Jun 23 '17 at 02:38

Code-Apprentice

81,660
23
145
268

I'm specifically trying to use the global variable though. I want the information to be stored there, not in a local variable to the function. – Kari Fox Jun 23 '17 at 02:47
@KariFox Because explicitly passing in the information that's required for a fucntion to run is good habit. It makes it clear when reading the function what data is, and isn't relevant to the operation of the function. Plus, manipulating globals is a bad habit. It leads to a lot of problems down the road. – Carcigenicate Jun 23 '17 at 02:52
@KariFox I agree with the above comment. Global variables are considered a bad programming practice. You should definitely take the time to learn how to pass values as parameters and return values from functions. You can make a program with these tools that gives the same results as trying to do this with globals. And the program will be better designed. – Code-Apprentice Jun 23 '17 at 02:57

score 1 · Answer 2 · answered Jun 23 '17 at 03:07

1

In your case, global an assigned variable within a function is strongly recommended.

#coding: utf-8

_str = ""

def test(var):
    global _str
    _str += var
    return _str

test("output")

answered Jun 23 '17 at 03:07

EUPHORAY

453
6
15

score 0 · Answer 3 · answered Jun 23 '17 at 02:53

use global password in the random_characters function.

So, for example,

password = ""
def random_characters(letters):
    global password
    add = random.choice(letters)
    password = password + add
letters_strong = string.ascii_letters + string.digits + string.punctuation
for i in range(16):
    random_characters(letters_strong)
print(password)

Using a global variable inside a function

3 Answers3