🎨 Python String Formatting – f-Strings, Format(), and % Explained
🧲 Introduction – Why String Formatting Matters
String formatting allows you to insert variables, numbers, and expressions into strings with clarity and control. It’s essential for generating readable messages, dynamic output, user-friendly logs, and cleanly structured data in Python.
Python supports multiple formatting styles, including:
- f-strings (modern, fast, Python 3.6+)
str.format()(versatile and widely used)%formatting (older but still supported)
🎯 In this guide, you’ll learn:
- How to format strings using f-strings,
format(), and% - Formatting numbers, dates, and alignment
- When to use each method
- Best practices for readability and maintainability
✳️ Method 1: f-Strings (Python 3.6+)
The most modern and readable approach.
name = "Alice"
age = 30
print(f"My name is {name} and I am {age} years old.")
✅ Supports expressions:
print(f"5 + 3 = {5 + 3}") # Output: 5 + 3 = 8
🔧 Method 2: str.format()
A flexible way to insert values into placeholders {}.
print("Hello, {}!".format("Bob"))
print("My name is {} and I am {}.".format("Alice", 30))
You can also reference by index or keyword:
print("Coordinates: {1}, {0}".format("Y", "X"))
print("Name: {name}, Age: {age}".format(name="Charlie", age=40))
🎯 Method 3: % Operator (Old Style)
This is an older syntax borrowed from C.
name = "David"
age = 25
print("My name is %s and I am %d years old." % (name, age))
💡 Still supported, but less readable and flexible than f-strings or .format().
🔢 Formatting Numbers
| Task | f-String Example | Output |
|---|---|---|
| 2 decimal places | f"{3.14159:.2f}" | 3.14 |
| Comma separator | f"{1000000:,}" | 1,000,000 |
| Leading zeros | f"{42:05}" | 00042 |
| Percentage | f"{0.25:.0%}" | 25% |
📅 Formatting Dates
With datetime module:
from datetime import datetime
now = datetime.now()
print(f"Today is {now:%Y-%m-%d %H:%M}")
✅ Output:
Today is 2025-05-13 20:00
🧠 String Alignment
You can align text using :> (right), :< (left), and :^ (center):
print(f"{'Name':<10}{'Age':>5}") # Output: Name Age
print(f"{'Alice':<10}{30:>5}") # Output: Alice 30
💡 Best Practices
- ✅ Use f-strings for readability and performance (Python 3.6+)
- ✅ Use
.format()when supporting Python 3.5 and below - ❌ Avoid
%unless maintaining legacy code - ✅ Use formatting for precision, alignment, and dynamic data injection
📌 Summary – Recap & Next Steps
Python offers multiple ways to format strings for readability, alignment, and data insertion. Mastering these tools helps you create cleaner outputs and more user-friendly applications.
🔍 Key Takeaways:
- ✅ Use
f-stringsfor modern and expressive formatting. - ✅ Use
.format()for backward compatibility. - ✅ Avoid
%unless maintaining legacy code. - ✅ Format numbers, dates, and alignments using rich syntax options.
⚙️ Real-World Relevance:
String formatting is critical in reports, logs, user interfaces, data exports, and template generation in both web and CLI apps.
❓ FAQ Section – Python String Formatting
❓ What is the best way to format strings in Python?
✅ f-strings are recommended for clarity, speed, and inline expression support (Python 3.6+).
❓ How can I format floating-point numbers to 2 decimal places?
✅ Use:
value = 3.14159
print(f"{value:.2f}") # Output: 3.14
❓ Can I align strings using f-strings?
✅ Yes! Use <, >, or ^ for left, right, and center alignment:
print(f"{'Name':<10}{'Age':>5}")
❓ Is % formatting still used in Python?
✅ It’s supported but discouraged in favor of f-strings and .format() for clarity and flexibility.
❓ How do I include variables inside a string?
✅ Use curly braces with f-strings:
name = "Alice"
print(f"Hello, {name}!")
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