Why Do Lambdas Within Loops in Python Share State?

Lambdas within Loops: Addressing Shared State

In Python, lambdas created within a loop can exhibit unexpected behavior due to shared state. As an example, consider the following code that aims to create lambdas that access an object's property:

lambdas_list = []
for obj in obj_list:
   lambdas_list.append(lambda : obj.some_var)

However, upon iterating through and calling these lambdas, the last object's property value is always obtained:

for f in lambdas_list:
    print(f())

To address this limitation, a simple modification can be made:

lambdas_list.append(lambda obj=obj: obj.some_var)

By providing a default argument to the lambda, the current value of the object is captured at the time of creation. This ensures that each lambda retains its own state, and the desired results are obtained:

for f in lambdas_list:
    print(f())

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