变量未更新/正在读取

Question

我很难弄清楚为什么"redo“变量在我的"check_user_input”函数运行后没有更新。确认它运行的消息总是会显示出来，但是依赖于"redo“的while循环永远不会运行。我不确定问题是变量没有更新，还是代码没有出于任何原因检查变量。这是我的密码：

import random 

redo = 0

def check_user_input(input):
    try:
        val = int(input)
    except ValueError:
        redo = 1
        print("Please enter a positive integer")
        
    
letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
numbers = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
symbols = ['!', '#', '$', '%', '&', '(', ')', '*', '+']

print("Welcome to the Password Generator!")

nr_letters= input("How many letters would you like in your password?\n")
check_user_input(nr_letters)
print ("redo:",redo)
while(redo == 1):
    nr_letters= input("How many letters would you like in your password?\n")
    check_user_input(nr_letters)

redo = 0
nr_symbols = input(f"How many symbols would you like?\n")
check_user_input(nr_symbols)
print ("redo:",redo)
while(redo == 1):
    nr_symbols = input("How many symbols would you like in your password?\n")
    check_user_input(nr_symbols)
    
redo = 0
nr_numbers = input(f"How many numbers would you like?\n")
check_user_input(nr_numbers)
print ("redo:",redo)
while(redo == 1):
    nr_numbers= input("How many numbers would you like in your password?\n")
    check_user_input(nr_numbers)

passwordlength = nr_letters + nr_numbers + nr_symbols


nr_letters = int(nr_letters)
nr_symbols = int(nr_symbols)
nr_numbers = int(nr_numbers)


chars = ""
for x in range (0, nr_letters): 
  char = random.choice(letters) 
  chars += char

nums = ""
for y in range (0, nr_numbers):
  num = random.choice(numbers)
  nums += num

syms = "" 
for z in range (0, nr_symbols): 
  symb = random.choice(symbols)
  syms += symb

print(f"Here is your password: {chars}{nums}{syms}")

Answer 1

check_user_input正在引用一个本地redo变量。如果要在顶层访问redo，则需要将global redo添加到check_user_input函数中，如下所示：

def check_user_input(input):
    global redo  # <-- This tells python to use the top level `redo` var
    try:
        val = int(input)
    except ValueError:
        redo = 1
        print("Please enter a positive integer")