I'm not sure how to fix this problem its saying f is not defined

Question

I'm trying to to create a password generator I'm trying to create the code bit in the form of functions but when I put the file reader part in a function its saying f is not defined

enter code here
num=int(input("enter how many characters you want in the password="))

def file_reader(f):
    #this is to creat a txt file and store the characters in it 
    f=open("guru99.txt","w+")
    f=f.write("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
    f=open("guru99.txt","r")
    f=f.read()
    f=list(f)
    return f 

def password_generator(num,f):
    #this is to pick random amount of characters from the list
    import random
    password=""
    for i in range(num):
        password+=random.choice(f)
    return password

#this is to run the functions
file_reader(f)
test=password_generator(num,f)
print(test)

Answer 1

I don't understand why you are writing and reading your characters to a file. You can simply choose a random character from a string like this:

num=int(input("enter how many characters you want in the password="))

f = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

def password_generator(num,f):
    #this is to pick random amount of characters from the list
    import random
    password=""
    for i in range(num):
        password+=random.choice(f)
    return password

#this is to run the functions
test=password_generator(num,f)
print(test)

This works in Python 3 (and 2).