Python Coding challenge - Day 573| What is the output of the following Python Code?

 

Code Explanation:

1. Function Definition

def tricky(val, result=[]):

Defines a function tricky with:

val: the value to add to a list.

result=[]: a default argument that is a mutable list.

2. Appending to the List

    result += [val]

result += [val] is equivalent to result.extend([val]).

It modifies the list in place, rather than creating a new list.

3. Return Statement

    return result

Returns the modified result list.

4. Function Calls & Output

print(tricky(1))

First call: val=1, result=[] (default list used).

result += [1] → result becomes [1].

Returns: [1].

print(tricky(2))

Second call: val=2, result is still the same list used in the first call ([1]).

result += [2] → result becomes [1, 2].

Returns: [1, 2].

print(tricky(3, []))

This time, a new list is passed explicitly as result=[].

result += [3] → becomes [3].

Returns: [3].

print(tricky(4))

Again, uses the original default list, which was mutated to [1, 2].

result += [4] → becomes [1, 2, 4].

Returns: [1, 2, 4].

Final Output

[1] [1, 2] [3] [1, 2, 4]

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