如何从def永久更改全局变量

Question

I am having problems updating and calling the value of a global variable.

I have tried looking up similar posts and articles on the internet. Also localising a small test which seems to run alright...however in this part of my overall code it doesn't work.

WEEK_ONE_REFINED = ""

def change_it():
    global WEEK_ONE_REFINED
    WEEK_ONE_REFINED = week_one_refined.strftime("%d/%m/%Y")

def print_it():
    print (WEEK_ONE_REFINED)

I have a global variable called WEEK_ONE_REFINED. I press a button and call change_it. I then press another button and call print_it but all it prints is the original "" value. Not the updated value.

Answer 1

Any reason why it needs to be global? This would be better:

def change_it(week_str):
    return week_str.strftime("%d/%m/%Y")

def print_it(week):
    print (week)

week = change_it("1/2/2019")
print_it(week)

Answer 2

You code is correct. If you are printing the original empty value, one of two things happens

• change_it is not called before print_it() (probably the button doesn't call it)
• the strftime expression provides an empty string (unlikely)

Answer 3

At first glance your code seems correct. I would say that your problem is that week_one_refined.strftime("%d/%m/%Y") is throwing an exception, and the variable never gets updated.

Answer 4

Sorry guys and thanks for all your help.

The function was linked to a checkbox and would only work if the checkbox was clicked. Once I began clicking the checkboxes the variables updated.

I have now fixed it so that the global variables are updated regardless of whether the checkboxes have been activated.

Thanks for all your help.