我应该如何编写带有数字扩展名的函数？ [复制]

Question

我正在尝试创建一个代码，其中包含一个函数，用于计算两个数字之间的随机数（我在编写代码时选择该随机数），然后将其从 Num1 中取出。但是，当我运行它时，它生成的数字总是0。请你告诉我如何正确编写这个函数！这是下面的代码。

import random
MinNum = int(0)
MaxNum = int(0)
Num1 = int(36)

def RandomNum(x,y,z):
    MinNum = x
    MaxNum = y
    Num1 = z
    Num1 = Num1 - random.randint(MinNum, MaxNum)

RandomNum(5,17,Num1) # - I would type it in the code like this
print(Num1) # - This should print a number that is equal to: 36 - the number generated.

Answer 1

您似乎对局部变量和全局变量感到困惑。要使RandomNum 能够更改Num1 的值，您需要将变量设为全局变量，否则，它将创建一个单独的Num1 变量，该变量仅适用于RandomNum 函数的持续时间。这称为作用域。

例如

def f():
    a = 2 # this a is local to the f() function.
    print('Inside of f (local scope), a =', a)

a = 1 # this is set in the global scope
f()
print('On the global level (global scope) a =', a) # Now that are f() function is finished, a will go back to being equal to 1

输出

在 f（局部范围）内，a = 2

在全局级别（全局范围）a = 1

但是，您可以将变量声明为全局变量，就像这样。

def f():
    global a # this time a will refer to the same variable inside and outside of our f() function
    a = 2
    print('Inside of f (local scope), a =', a)

a = 1
f()
print('On the global level (global scope) a =', a)

然后你得到

在 f（局部范围）内，a = 2

在全局级别（全局范围）a = 2

如果我们将此应用到您的代码中，我们可以像这样修复它。

import random
MinNum = int(0)
MaxNum = int(0)
Num1 = int(36)

def RandomNum(x,y,z):
    global MinNum, MaxNum, Num1
    MinNum = x
    MaxNum = y
    Num1 = z
    Num1 = Num1 - random.randint(MinNum, MaxNum)

RandomNum(5,17,Num1)
print(Num1)

然而，让函数返回一些东西而不是操作全局变量更为常见。你的函数也可以这样重写。

import random

def RandomNum(minNum, maxNum, subtractedFrom):
    return subtractedFrom - random.randint(minNum, maxNum)

num1 = RandomNum(5, 17, 36)
print(result)

虽然确实没有理由首先拥有这个功能，因为RandomNum(5, 17, 36) 与random.randint(19, 31) 是一样的，所以你的代码可以简单地写成

import random
print( random.randint(19, 31) )