Python中random.choice()在函数内报错的问题求助

问题描述 #

原本可正常运行的密码生成代码，封装到函数后调用random.choice()时出现以下错误：

TypeError: object of type 'int' has no len()

正常运行的代码 #

import random
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("Password Generator")
user_amount_letters = int(input("How many letters would you like in your password?\n")) 
user_amount_symbols = int(input("How many symbols?\n"))
user_amount_numbers = int(input("How many numbers\n"))

characters = []

for i in range(user_amount_letters):
  characters.append(random.choice(letters))
for i in range(user_amount_numbers):
  characters.append(random.choice(numbers))
for i in range(user_amount_symbols):
  characters.append(random.choice(symbols))

random.shuffle(characters)
password = "".join(characters)
print(password)

封装后报错的函数代码 #

def randomise_user_password(letters, symbols, numbers):
  user_letters = letters
  user_symbols = symbols
  user_numbers = numbers
  characters = []
  
  for i in range(user_letters):
    characters.append(random.choice(letters))
  for i in range(user_numbers):
    characters.append(random.choice(numbers))
  for i in range(user_symbols):
    characters.append(random.choice(symbols))

  random.shuffle(characters)
  password = "".join(characters)
  return password


print(randomise_user_password(user_amount_letters, user_amount_symbols, user_amount_numbers))

错误原因 #

函数参数名和全局定义的字符列表变量名完全重名了：

• 函数参数定义为letters, symbols, numbers，但调用时传入的是user_amount_letters等整数类型的计数变量
• 函数内部random.choice(letters)中的letters已经被覆盖成传入的整数，而非原来的字符列表
• random.choice()需要接收可迭代序列（如列表）来获取长度，整数没有len()方法，因此触发报错

修正后的代码 #

import random
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("Password Generator")
user_amount_letters = int(input("How many letters would you like in your password?\n")) 
user_amount_symbols = int(input("How many symbols?\n"))
user_amount_numbers = int(input("How many numbers\n"))

def randomise_user_password(letter_count, symbol_count, number_count):
    characters = []
    
    for i in range(letter_count):
        characters.append(random.choice(letters))
    for i in range(number_count):
        characters.append(random.choice(numbers))
    for i in range(symbol_count):
        characters.append(random.choice(symbols))

    random.shuffle(characters)
    password = "".join(characters)
    return password

print(randomise_user_password(user_amount_letters, user_amount_symbols, user_amount_numbers))

修改说明 #

• 将函数参数名改为letter_count, symbol_count, number_count，避免和全局字符列表变量名冲突
• 函数内部循环时使用这些计数参数，调用random.choice()时仍引用全局定义的letters, symbols, numbers列表，确保传入的是正确的序列对象

内容的提问来源于stack exchange，提问作者Cwisfa