Variable referenced before assignemnt in for loop-CodePudding

I just started working with loops and somehow this is giving me an error, something with the variable pw is not right but I don't see anything wrong with it.

import random
import string

letters= string.printable
length= int(input( "How long do you want your password to be? "))

pw= ""

def generatePass():
  for i in range(length):
    pw = pw   random.choice(letters) #Error here
print(pw)

generatePass()

Any help is appreciated Nick

CodePudding user response：

Your problem is not in the loop, but in the communication between your function (def generatePass) and your main execution. The following works:

import random
import string
letters= string.printable

def generatePass(length):
    pw = ""
    for i in range(length):
        pw = pw   random.choice(letters) #Error here
    return pw


length= int(input( "How long do you want your password to be? "))

print(generatePass(length))

CodePudding user response：

So the thing is that pw variable is not in your function. generatePass does not see it. In python, functions can't access any variable outside of the function unless its a parameter or is declared global. So there are 3 ways that you can make your code working:

Pass pw as a parameter to your function:

import random
import string

letters = string.printable
length = int(input("How long do you want your password to be? "))

pw = ""


def generatePass(pw):
    for i in range(length):
        pw = pw   random.choice(letters)
    return pw


print(generatePass(pw)) # here you pass the variable to a function

Create local varialbe pw inside the generatePass function:

import random
import string

letters = string.printable
length = int(input("How long do you want your password to be? "))


def generatePass():
    pw = "" # here you create local variable inside a function (it is not visible outside of it)
    for i in range(length):
        pw = pw   random.choice(letters)
    return pw


print(generatePass())

Thanks to it you do not have to pass pw as a parameter to a function.

Make your variable global

import random
import string

letters = string.printable
length = int(input("How long do you want your password to be? "))

pw = ""


def generatePass():
    global pw # here you make pw as a global variable
    for i in range(length):
        pw = pw   random.choice(letters)
    return pw


generatePass()
print(pw)