Create different functions from loop in Python

Question

I’m trying to build a tkinter GUI, and I’m having a Python programming logic issue. My problem is the following: I’m creating a bunch of objects in the following way:

class Aplication:
    def createObjects(self):
        objects = []
        for i in range(10):
            obj = Object(command = lambda: self.myFunction(i))
            objects.append(obj)

    def myFunction(self, i):
        print(i)

And when executing each object’s command I expected the result:

But instead I’m getting:

I simplified my code so that anyone who knows Python logic can help me.
Appreciate any help in advance.

Asked By: Gustavo Exel

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Source

Answer 1

This slightly modified version works as you expect.

It is essentially the variable scope problem.
In your implementation, the function looks for i in the runtime, when i has already been updated to 9.
If you want to keep the "current" value of i, you need to define a function with the current i like below.

class Object:
    def __init__(self, command):
        self.command = command
        
class Application:
    def createObjects(self):
        objects = []
        for i in range(10):
            obj = Object(command = self.myFunction(i))
            objects.append(obj)
        return objects
    
    def myFunction(self, i):
        return lambda: print(i)

a = Application()
os = a.createObjects()
for o in os:
    o.command()

Answered By: Kota Mori

Create different functions from loop in Python

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