Global variable is undefined at the module level

[Daiyue Weng]

Hi, I defined a global variable in some function like this,

def some_function(self):

global global_var

PyCharm inspection gave me,

Global variable is undefined at the module level

How to fix this?

cheers

[Peter Otten]

Daiyue Weng wrote:

> Hi, I defined a global variable in some function like this,
>
> def some_function(self):
>
> global global_var
>
> PyCharm inspection gave me,
>
> Global variable is undefined at the module level

There is no single way to silence that complaint and actually improve your
code; you have to provide some context: Why do you need a global at all, why
can't you (or don't want to) bind it on the module level etc.

[Ned Batchelder]

It probably wants you to have a line at the top-level of the module (outside of any function) defining the variable:

global_var = None # or some other default value

--Ned.

[dieter]

Daiyue Weng <daiyu...@gmail.com> writes:

> Hi, I defined a global variable in some function like this,
>
> def some_function(self):
>
> global global_var
>
> PyCharm inspection gave me,
>
> Global variable is undefined at the module level
>
> How to fix this?

You define the global variable at the module level.

"global VVV" (in a function) actually does not define "VVV"
as a global variable. Instead, it tells the interpreter that
"VVV" should not be treated as a local variable but be looked up
in the "global" (usually module) namespace.

In order to define "VVV", you must assign a value to it -- either
directly in the "global" (i.e. module) namespace or in your function
(together with a "global VVV" declaration).

[jackson...@gmail.com]

This is not accurate. I just tested this in python3 and using the global keyword allowed me to declare a variable inside the function that was then visible from the outer scope.

[Pieter van Oostrum]

jackson...@gmail.com writes:

> This is not accurate. I just tested this in python3 and using the global
> keyword allowed me to declare a variable inside the function that was
> then visible from the outer scope.

What do you mean by that?
Anything other than what was said here?

> On Tuesday, September 13, 2016 at 6:50:39 AM UTC-5, dieter wrote:

>> In order to define "VVV", you must assign a value to it -- either
>> directly in the "global" (i.e. module) namespace or in your function
>> (together with a "global VVV" declaration).

Without assignment the variable will not exist in the module namespace:
>>> def testfunc():
... global globvar
... pass
...
>>> globvar
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'globvar' is not defined
>>> testfunc()
>>> globvar
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'globvar' is not defined

>>> def testfunc():
... global globvar
... globvar = 1
...
>>> globvar
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'globvar' is not defined
>>> testfunc()
>>> globvar
1


--
Pieter van Oostrum
www: http://pieter.vanoostrum.org/
PGP key: [8DAE142BE17999C4]