javascript - 在Python中使用函数声明全局变量

Question

这段 JavaScript 代码运行良好。我的问题不在于修复代码本身，而在于如何在 Python 中模仿它。

function setupSomeGlobals() {
    // Local variable that ends up within closure
    var num = 666;
    // Store some references to functions as global variables
    gAlertNumber = function() { alert(num); }
    gIncreaseNumber = function() { num++; }
    gSetNumber = function(x) { num = x; }
}

当调用setupSomeGlobals()时，它会声明要全局使用的新函数。这可以在Python中以某种方式模仿吗？我不知道怎么办。 Python 函数似乎并不像 JavaScript 函数那样运行，因为任何全局的东西都需要以某种方式返回。

Answer 1

根据不要在实际代码中执行此操作的标准免责声明，您的 Javascript 的 Python (3) 翻译将如下所示:

def setup_some_globals():
    # Local variable
    num = 666

    # You have to explicitly declare variables to be global, 
    # otherwise they are local.
    global alert_number, increase_number, set_number

    def alert_number():
        # You can read a variable from an enclosing scope 
        # without doing anything special
        print(num)

    def increase_number():
        # But if you want to assign to it, you need to be explicit about 
        # it. `nonlocal` means "in an enclosing scope, but not 
        # global".
        nonlocal num
        num += 1

    def set_number(x):
        # Same as above
        nonlocal num
        num = x

# Usage:
>>> setup_some_globals()
>>> set_number(3)
>>> increase_number()
>>> alert_number()
4

Docs for nonlocal statement

Docs for global statement

但如果您确实这样做，那么几乎肯定有更好的方法来完成您想做的事情。