Python Coding challenge - Day 240 | What is the output of the following Python Code?

 

def func(x=[]):

    x.append(1)

    return x

print(func())

print(func())

Solution and Explanation: B is the correct answer

Default Argument Behavior:

The default argument x=[] is evaluated only once when the function is defined, not each time the function is called. This means that if the default value is a mutable object like a list, it will be shared across all calls to the function.

First Function Call (print(func())):

The first time func() is called, the list x is empty because the default value ([]) is used.

Inside the function, 1 is appended to the list, so x becomes [1].

The function returns this list, which is then printed, so the output is:

Second Function Call (print(func())):

The second time func() is called, the same list x from the previous call is used, not a new empty list.

Again, 1 is appended to this list, so x becomes [1, 1].

The function returns this list, which is then printed, so the output is:

[1, 1]

Mutable Default Arguments: In Python, using a mutable object (like a list or dictionary) as a default argument can lead to unexpected behavior because it persists across function calls.

Best Practice: To avoid this, use None as the default value and then initialize the mutable object inside the function if needed.