6 Beginner Mistakes in Python and How To Fix Them

1. Misusing Indentation

The Mistake:
Python is strict about indentation, and early on, I accidentally mixed tabs and spaces in my code.

The Fix:
I configured my code editor to use spaces instead of tabs (4 spaces per indentation level). I also enabled a “show whitespace” option to catch accidental formatting errors early.

Lesson Learned: Always be consistent with your indentation style.

2. Confusing Mutable and Immutable Data Types

The Mistake:
I tried to modify a tuple, only to get a TypeError. Later, I accidentally modified a list that I didn’t mean to, leading to unexpected behavior in my code.

The Fix:
I learned the distinction between mutable (e.g., lists, dictionaries) and immutable (e.g., tuples, strings) data types. When I needed to keep data unchanged, I started using tuples or frozenset.

Lesson Learned: Understand the difference between mutable and immutable types to avoid unintended consequences.

3. Forgetting to Initialize Variables

The Mistake:
I attempted to use a variable before assigning it a value, which caused a NameError.

The Fix:
To prevent this, I adopted a habit of initializing variables with default values when declaring them. For example:

Instead of:

print(total)  # NameError: name 'total' is not defined  

Do this:

total = 0  
print(total)

Lesson Learned: Always initialize variables before using them.

4. Overwriting Built-In Function Names

The Mistake:
I named a variable list in one of my scripts, which overwrote Python’s built-in list function. This caused issues when I later tried to use list() to create a new list.

The Fix:
I became more mindful of variable names and avoided using names that clash with Python’s built-in functions. Tools like linters also helped me catch these mistakes before running the code.

Lesson Learned: Avoid using Python’s reserved words and built-in function names as variable names.

5. Not Using List Comprehensions

The Mistake:
I used long, nested for loops to create new lists, which made my code harder to read and less efficient.

The Fix:
I learned about list comprehensions and started using them for concise and readable code. For example:

Instead of:

squared_numbers = []  
for num in range(10):  
    squared_numbers.append(num ** 2) 

Do this:

squared_numbers = [num ** 2 for num in range(10)]

Lesson Learned: Embrace Pythonic constructs like list comprehensions for cleaner and faster code.

6. Not Using F-Strings for String Formatting

The Mistake:
I used older string formatting methods like % or .format(), which were less readable and sometimes error-prone.

The Fix:
I switched to f-strings for cleaner and more intuitive formatting. For example:

Instead of:

print("Hello, {}!".format(name))  

Do this:

print(f"Hello, {name}!")  

Lesson Learned: F-strings (introduced in Python 3.6) are a game-changer for readable and efficient string formatting.

Final Thoughts

Mistakes are an essential part of learning, especially when it comes to programming. While these early missteps were frustrating, they helped me grow as a Python developer. If you’re just starting out, remember to embrace your mistakes—they’re stepping stones to success.

What beginner mistakes have you made while coding? Share your experiences in the comments below!