Set a variable from a class within a different file

Question

I have 2 files:

fileA.py

and

fileB.py

I am trying to set (change) a variable from fileA from a function within fileB. The variable I'm trying to change is inside of a class (I believe the variable is a Class variable). I tried importing fileA inside of fileB but got errors.

# fileA:
...
class SomeDialog(QDialog):
    my_var = 0
...


# fileB:
...
from fileA import SomeDialog as sd
    def my_func():
        sd.my_var = 5
...

Any help?

ImportError: cannot import name 'SomeDialog' – shafuq Mar 24 '18 at 14:05 — shafuq, Mar 24 '18 at 14:05

score 1 · Answer 1 · answered Mar 24 '18 at 14:10

1

According to the error you got, you probably have circular import somewhere. It is not related to what you are trying to do with your classes.

See ImportError: Cannot import name X for more details

If that's the case, the only way to solve it is to change your file structures.

answered Mar 24 '18 at 14:10

Mia

2,466
22
38

Even if you're right (and you might be), it doesn't answer the question of how to change a class variable from another file. The answers here are for instance changes. I'm looking for an alternative way of doing this.. – shafuq Mar 24 '18 at 14:36
@Mr.Robot The method you are using appear to be right. I tested on my computer and it's working. – Mia Mar 24 '18 at 14:41

score 0 · Answer 2 · answered Mar 24 '18 at 13:51

0

Your class should look like this:

class SomeDialog(QDialog):
    def __init__(self):
        self.my_var = 0

Then you can access the my_var like this:

SomeDialog.my_var

answered Mar 24 '18 at 13:51

Gleb Koval

149
1
10

This is a large program with thousands of lines. I have that variable used in lots of places and it is defined before init. BTW is your answer for an instance variable? – shafuq Mar 24 '18 at 13:54
@Mr.Robot You could make it an instance variable – Gleb Koval Mar 24 '18 at 14:08
The thing is I can't. it is important that it stays as a class variable for the program. The value has to always be constant within the different instances. I'm looking for an answer for the way it is shown above. – shafuq Mar 24 '18 at 14:12
Ok, sorry then, I cannot help you – Gleb Koval Mar 24 '18 at 14:15

score 0 · Answer 3 · answered May 06 '19 at 10:47

Class variables are defined within a class but outside any of the class's methods. Class variables are not used. class variables have the same value across all class instances

A.py

from B import SomeDialog as sd
def my_func():
    print sd.my_var
    sd.my_var = 5
    return sd 
_my_func = my_func()
print _my_func.my_var

B.py

class SomeDialog(object):
    my_var = 0

#output

0
5

Set a variable from a class within a different file

3 Answers3