这是两种实现相同目的的方法：

使用参数并返回（推荐）

def other_function(parameter):
    return parameter + 5

def main_function():
    x = 10
    print(x)    
    x = other_function(x)
    print(x)

运行时main_function，将获得以下输出

>>> 10
>>> 15

使用全局变量（永远不要这样做）

x = 0   # The initial value of x, with global scope

def other_function():
    global x
    x = x + 5

def main_function():
    print(x)    # Just printing - no need to declare global yet
    global x   # So we can change the global x
    x = 10
    print(x)
    other_function()
    print(x)

现在您将获得：

>>> 0    # Initial global value
>>> 10   # Now we've set it to 10 in `main_function()`
>>> 15   # Now we've added 5 in `other_function()`