[Solved] Identify the bug in this polymorphic function:def combine(a, b): if isinstance(a, list) and isinstance(b, list): return a + b elif isinstance(a, dict) and isinstance(b, dict): return {**a, **b} else:... | Python

Python - Polymorphism and Dynamic Behavior

Identify the bug in this polymorphic function:

def combine(a, b):
    if isinstance(a, list) and isinstance(b, list):
        return a + b
    elif isinstance(a, dict) and isinstance(b, dict):
        return {**a, **b}
    else:
        return a.append(b)

ALists cannot be added with + operator

Bappend modifies list in place and returns None, causing unexpected output

CCannot use ** to merge dictionaries

DFunction lacks return statement in else

Step-by-Step Solution

Solution:

Step 1: Understand list append behavior
append() changes list but returns None, so returning a.append(b) returns None.
Step 2: Check other parts
Using + for lists and ** for dicts is correct. Else branch returns None unexpectedly.
Final Answer:
append modifies list in place and returns None, causing unexpected output -> Option B
Quick Check:
append returns None, so returning it causes bugs [OK]

Quick Trick: append returns None; don't return it directly [OK]

Common Mistakes:

Returning append() result instead of list
Thinking ** cannot merge dicts
Confusing list addition with append

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Identify the bug in this polymorphic function:

Step 1: Understand list append behavior

Step 2: Check other parts

Final Answer:

Quick Check:

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