Python: Unresolved Reference (variableName) when trying to refer to and use variables I declared at the top of the script, within a function

Question

I declare these variables at the start of my python script:

hours = 0
mins = 0
secs = 0

Then I create a function, and want to make use of those variables within my function:

def calc_running_total():
    hours = hours + int(running_total[0:2])
    mins = mins + int(running_total[3:5])
    if mins == 60 or mins > 60:
        hours += 1
        mins = mins - 60
    secs = secs + int(running_total[6:8])
    if secs == 60 or secs > 60:
        mins += 1
        secs = secs - 60

But it underlines hours, mins and secs after the assignment operator (=) in red, and says "Unresolved reference: Hours" and same for mins and secs.

How do I make use of variables declared at the top of my script within functions?

Thanks.

EDIT: I've been told to put "global hours" within the function definition. But I don't have to do that for another function I've just defined, with variable "activity_type":

def add_to_correct_list():
    if activity_type.casefold() == "work":
        if day_and_date:
            work_list.append((day_and_date))
            print(f"\n{day_and_date} added to work_list")
        work_list.append(activity_item_name + ": " + running_total)
        print("\nItem and time tracking added to Work_List!")

Why don't I need to do that in this function?

Does this answer your question? [Short description of the scoping rules?](https://stackoverflow.com/questions/291978/short-description-of-the-scoping-rules) — MisterMiyagi, Jul 31 '20 at 19:01
Can you clarify your last sub-question? ``add_to_correct_list`` does not use ``hours``, ``mins`` or ``secs``. Most importantly, it does not assign to any variable. — MisterMiyagi, Jul 31 '20 at 19:03
"activity_type" does not need a "global activity_type" statement in this function. Is it because it has no assignment associated with it within the function? — Eskimo4, Jul 31 '20 at 19:29

Alec · Accepted Answer · 2020-07-31T21:36:11.663

2

# these are considered 'global vars'
hours = 0
mins = 0
secs = 0


def calc_running_total():
    global hours  # now the method will reference the global vars
    global mins
    global secs
    hours = hours + int(running_total[0:2])
    mins = mins + int(running_total[3:5])
    if mins == 60 or mins > 60:
        hours += 1
        mins = mins - 60
    secs = secs + int(running_total[6:8])
    if secs == 60 or secs > 60:
        mins += 1
        secs = secs - 60

Other examples as requested:

hours = 1
def implicit_global():
    print(hours)  # 1

hours = 1
def point_to_global():
    global hours
    print(hours)  # 1
    print(hours+ 1)  # 2

print(hours)  # 2

hours = 1
def implicit_global_to_local():
    local_hours = hours  # copies the global var and sets as a local var
    print(local_hours)  # 1
    print(local_hours + 1)  # 2

print(hours)  # 1

edited Jul 31 '20 at 21:36

answered Jul 31 '20 at 18:29

Alec

137
4

Thanks, but is that the only way? To have to write "global previouslyDeclaredVariableName" each time? – Eskimo4 Jul 31 '20 at 18:47
No, it's not the only way. You could start with ```hours = hours```, but the way described is more explicit, which avoids confusion. – Alec Jul 31 '20 at 21:28
@Eskimo4 -- added a few more examples, since the alternatives will have side effects. – Alec Jul 31 '20 at 21:36

Python: Unresolved Reference (variableName) when trying to refer to and use variables I declared at the top of the script, within a function

1 Answers1