SyntaxError:在Python3.6中的全局声明之前将名称"cows"分配给了 [英] SyntaxError: name 'cows' is assigned to before global declaration in Python3.6

问题描述

我正在尝试在循环内编辑全局变量cows和bulls，但出现此错误"SyntaxError: name 'cows' is assigned to before global declaration"

I am trying to edit the global variables cows and bulls inside a loop but getting this error "SyntaxError: name 'cows' is assigned to before global declaration"

import random

random_no = random.sample(range(0, 10), 4)
cows = 0
bulls = 0
#random_num = ','.join(map(str, random_no))
print(random_no)
user_input = input("Guess the no: ")
for index, num in enumerate(random_no):
    global cows, bulls
    print(index, num)
    if user_input[index] == num:
        cows += 1
    elif user_input[index] in random_no:
        bulls += 1

print(f'{cows} cows and {bulls} bulls')

推荐答案

Python没有块作用域，只有函数和类引入了新的作用域.

Python has no block scoping, only functions and classes introduce a new scope.

因为这里没有功能，所以不需要使用global语句，cows和bulls已经已经为全局变量.

Because you have no function here, there is no need to use a global statement, cows and bulls are already globals.

您还有其他问题:

• input()始终返回一个字符串.

• input() returns a string, always.

索引适用于字符串(您会得到单个字符)，确定要这样做吗?

Indexing works on strings (you get individual characters), are you sure you wanted that?

user_input[index] == num始终为假； '1' == 1测试两种不同类型的对象是否相等；他们不是.

user_input[index] == num is always going to be false; '1' == 1 tests if two different types of objects are equal; they are not.

user_input[index] in random_no也总是会为假，您的random_no列表仅包含整数，没有字符串.

user_input[index] in random_no is also always going to be false, your random_no list contains only integers, no strings.

如果用户要输入一个随机数，请将input()转换为整数，而不必理会enumerate():

If the user is to enter one random number, convert the input() to an integer, and don't bother with enumerate():

user_input = int(input("Guess the no: "))
for num in random_no:
    if user_input == num:
        cows += 1
    elif user_input in random_no:
        bulls += 1

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