witfame

1. ❌ Using Mutable Default Arguments

def add_item(item, item_list=[]):
    item_list.append(item)
    return item_list

• Problem: item_list retains values across multiple calls.
• Fix:

def add_item(item, item_list=None):
    if item_list is None:
        item_list = []
    item_list.append(item)
    return item_list

2. ❌ Not Using List Comprehensions When Appropriate

squared = []
for i in range(10):
    squared.append(i ** 2)

• Better:

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

3. ❌ Misunderstanding is vs ==

a = [1, 2, 3]
b = [1, 2, 3]
print(a is b)   # False
print(a == b)   # True

• Use == for value comparison, is for identity comparison (same object in memory).

4. ❌ Importing Everything from a Module

from math import *

• Problem: Clutters namespace, risk of name collisions.
• Fix:

import math
print(math.sqrt(9))

5. ❌ Ignoring Exceptions or Catching Broad Exceptions

try:
    risky_operation()
except Exception:
    pass  # Silent fail – bad practice!

• Fix:

try:
    risky_operation()
except ValueError as e:
    print(f"Value error: {e}")

6. ❌ Not Using Virtual Environments

• Leads to dependency conflicts.
• Fix:

python -m venv venv
source venv/bin/activate  # Linux/Mac
venv\Scripts\activate     # Windows

7. ❌ Using print() for Debugging in Production Code

• Use the logging module instead:

import logging
logging.basicConfig(level=logging.INFO)
logging.info("This is an info message")

8. ❌ Misusing Global Variables

counter = 0

def increment():
    counter += 1  # Error: UnboundLocalError

• Fix:

def increment():
    global counter
    counter += 1

9. ❌ Overcomplicating with Loops When You Can Use map, filter, or zip

names = ['Alice', 'Bob']
ages = [24, 27]
for i in range(len(names)):
    print(names[i], ages[i])

• Better:

for name, age in zip(names, ages):
    print(name, age)

10. ❌ Forgetting to Close Files (Before Using Context Manager)

file = open('data.txt')
data = file.read()
file.close()

• Fix (Recommended):

with open('data.txt') as file:
    data = file.read()

✅ Bonus Tips

• Use type hints for better readability and tooling:

def add(x: int, y: int) -> int:
    return x + y

• Use tools like Black, Flake8, and Pylint to format and lint your code.
• Write unit tests using unittest or pytest.