Python Coding challenge - Day 488| What is the output of the following Python Code?

 

Code Explanation:

1. Function Definition

def add_entry(key, value, data={}):

Function Name: add_entry

Parameters:

key: The key to add to the dictionary.

value: The value to assign to the key.

data={}: A mutable default argument — this is important and causes unexpected behavior.

2. Function Logic

data[key] = value

return data

The function adds the key-value pair to the data dictionary.

Then it returns the updated dictionary.

3. Function Calls

print(add_entry('a', 1))

print(add_entry('b', 2))

This is where the mutable default argument issue shows up.

 4. What Happens Internally

First Call:

add_entry('a', 1)

data is the default {}.

'a': 1 is added.

Returns: {'a': 1}

Second Call:

add_entry('b', 2)

You might expect a new dictionary, but Python reuses the same data dictionary from the previous call.

'b': 2 is added to the same dictionary.

Returns: {'a': 1, 'b': 2}

5. Output

{'a': 1}

{'a': 1, 'b': 2}