Why Comments Matter in Python

Imagine coming back to your code after months and seeing this:

“`python
x = 10 * y + z / (a ** 2)

**What does it do?** Without comments, even *you* might forget.  

Comments are **notes in your code** that:  
✔️ Explain complex logic  
✔️ Help others understand your work  
✔️ Temporarily disable code without deleting it  

Here’s how to write them in Python—the right way.  

---  

## **Method 1: Single-Line Comments (Most Common)**  

Use the **`#` symbol** for short notes:  

python

Calculate total price with tax

total = price * 1.08 # 8% sales tax

✅ **Best for:** Quick explanations or disabling a line.  

---  

## **Method 2: Multi-Line Comments**  

Python doesn’t have a direct multi-line comment syntax, but you can:  

### **Option 1: Use Multiple `#` Lines**  

python

This function calculates the

area of a circle.

Formula: π * radius²

def circle_area(radius):
return 3.14 * (radius ** 2)

### **Option 2: Use Triple Quotes (For Docstrings)**  

python
“””
This script processes user data.
Steps:

1. Load data from CSV
2. Clean missing values
3. Export to database
   “””

⚠️ **Note:** Triple quotes are *technically* strings, but they work as comments if not assigned to a variable.  

---  

## **Method 3: Inline Comments (For Clarity)**  

Place comments **beside code** to explain tricky parts:  

python
speed = distance / time # meters per second (m/s)

🚫 **Avoid obvious comments like:**  

python
x = 5 # Set x to 5

---  

## **Python Commenting Best Practices**  

1. **Explain *why*, not *what***:  
   - ❌ Bad: `x = x + 1  # Increment x`  
   - ✅ Good: `x = x + 1  # Adjust for offset index`  

2. **Use docstrings for functions**:  

python
def calculate_interest(principal, rate):
“””
Calculates annual compound interest.
Args:
principal (float): Initial amount
rate (float): Interest rate (e.g., 0.05 for 5%)
“””
return principal * (1 + rate)

3. **Keep comments updated** (outdated comments confuse more than no comments!).  

---  

## **How to Temporarily Disable Code**  

Comment out lines to **test/debug without deleting**:  

python

print(“Debug: Current value is”, x)

x = process_data(x)
“`

Write Code Humans Can Understand

Comments turn your Python script from this:

result = (a - b) / c * 100

Into this:

# Calculate percentage change from baseline
result = (a - b) / c * 100

Remember: Good code explains itself—but great code uses comments where needed.

(This content has been updated in August 2025)

Now you know how to comment in Python—happy coding!

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