Python - overwrite variable from another class?

Question

Simple question that i cant figure out: I have (example) file one with this:

class foo:
var = 1
def bar(self):
 print(self.var)
if __name__ == "__main__":
 foo().bar()

and file2 with this:

from testing import foo
class foo2:
 def bar2(self):
 foo().var = 2
 foo().bar()
foo2().bar2()

It returns 1, so no overwriting happening here.

I cant figure out how to actually overwrite the variable of the imported class instance. I checked this and this but that didnt help me. Sorry for asking such a simple question, thanks in advance.

• Guillaume: foo is a class, foo() is an instance. You seems to mix those notions.
• Guillaume: Possible duplicate of python: class attributes and instance attributes
• Flying Thunder: But i created an instance in file2 didnt i? What would the working code have changed?

Answer 1

It is being overwritten, but you're discarding the object immediately. foo().var = 2 creates an anonymous foo object, and assigns it's var to 2. The problem is you're not keeping a reference to the foo object you've just created. Then, foo().bar() creates a new foo object, which has var == 1 (just like all new foo objects since that's what your class does) and also calls the bar() member function on this new foo object, which will print 1 to console.

Try this instead:

def bar2(self):
 foo_obj = foo()
 foo_obj.var = 2
 foo_obj.bar()

• Flying Thunder: Damn, i just came back to python and the difference between foo, foo() and f1=foo() always confused me. Thanks! Additional question: Are there cases where what i did ("annymous" asignment) are ever useful?

Answer 2

When you're doing foo().bar() , you're creating a second instance.

Try this:

 test = foo()
 test.var = 2
 test.bar()
 # foo().var = 2
 # foo().bar()