Python如何修改全局变量

Question

我希望能够得到上传成功的确认，我已经定义了类似以下代码的方法。但是全局变量的值并没有改变，请帮忙解决。

global upload_confirm
upload_confirm = False

def confirm_upload():
    upload_confirm = True

def start_new_upload():
    confirm_upload()
    while (upload_confirm != True):
        print "waiting for upload to be true"
        time.sleep(5)
    if (upload_confirm == True):
        print "start Upload"

start_new_upload()

- Anup Singh

Answer 1

你可以尝试这样做：

def confirm_upload():
    global upload_confirm
    upload_confirm = True

由于你在局部作用域中使用了upload_confirm = True，Python将其视为局部变量。因此，全局变量保持不变。

- Pablo Santa Cruz

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如果我只想读取全局变量，是否可以跳过每个函数开头的“global”声明？ - SomethingSomething

Answer 2

您需要在希望访问全局变量的作用域中放置 global 语句，例如：

upload_confirm = False

def confirm_upload():
    global upload_confirm
    upload_confirm = True

- poke

Answer 3

在您的confirm_upload()方法中尝试这个。

def confirm_upload():
    global upload_confirm #Add this line
    upload_confirm = True

如果你不在方法内声明它为全局变量，它默认是局部变量。

- venki421

Answer 4

global语句应该在函数内部。

def confirm_upload():
    global upload_confirm
    upload_confirm = True

否则，upload_confirm = .. 将会创建一个本地变量。

- falsetru