4 Python Mistakes That Make You Look Like a Beginner (And How to Avoid Them)

 1. Using Mutable Default Arguments

Mistake:

def add_item(item, items=[]):

    items.append(item)

    return items

Problem: Default mutable arguments, like lists or dictionaries, retain changes between function calls, which can lead to unexpected behavior.

Fix:

def add_item(item, items=None):

    if items is None:

        items = []

    items.append(item)

    return items

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2. Not Using List Comprehensions

Mistake:

result = []

for i in range(10):

    result.append(i * 2)

Problem: This approach is verbose and less efficient than it could be.

Fix:

result = [i * 2 for i in range(10)]

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Explanation: List comprehensions are more Pythonic, concise, and often faster.

3. Misunderstanding Python’s Scope Rules (LEGB Rule)

Mistake:

x = 10

def example():

    print(x)

    x = 5

example()

Problem: This raises an UnboundLocalError because Python considers x inside example() as a local variable due to the assignment.

Fix:

x = 10

def example():

    global x

    print(x)

    x = 5

example()

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4. Using print() for Debugging Instead of Proper Debugging Tools

Mistake:

def calculate(x):

    print(f"Debug: x = {x}")

    return x * 2

result = calculate(5)

Problem: Relying on print() statements for debugging can clutter code and is less efficient.

Fix:

def calculate(x):

    return x * 2

result = calculate(5)

# Use a debugger for inspection

import pdb; pdb.set_trace()

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