String Formatting in Python

Python provides multiple ways to format strings efficiently. Below are different string formatting techniques with examples.

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1. f-strings (Formatted String Literals) – Best & Fastest

Introduced in Python 3.6, f-strings allow embedding expressions inside {} directly within a string.

name = "Gaurav"
age = 22
print(f"My name is {name} and I am {age} years old.")

Output:

My name is Gaurav and I am 22 years old.

✅ Supports expressions inside {}
✅ Fastest method
✅ Readable & concise

(a) Evaluating Expressions inside f-strings

num1, num2 = 10, 5
print(f"Sum: {num1 + num2}")  # Sum: 15

(b) Using Functions inside f-strings

def square(x):
    return x * x

print(f"Square of 4 is {square(4)}")  # Square of 4 is 16

(c) Formatting Numbers using f-strings

pi = 3.1415926535
print(f"Pi rounded: {pi:.2f}")  # Pi rounded: 3.14
print(f"Formatted number: {1000000:,}")  # 1,000,000

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2. .format() Method – Versatile but Verbose

The .format() method allows positional and named placeholders.

name = "Gaurav"
age = 22
print("My name is {} and I am {} years old.".format(name, age))

(a) Positional & Named Placeholders

print("Hello, {0}. You are {1} years old.".format("Gaurav", 22))
print("Hello, {name}. You are {age} years old.".format(name="Gaurav", age=22))

(b) Number Formatting in .format()

pi = 3.1415926535
print("Pi: {:.2f}".format(pi))  # Pi: 3.14

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3. % Formatting (Old Style, Similar to C)

Older method, less readable but works in all Python versions.

name = "Gaurav"
age = 22
print("My name is %s and I am %d years old." % (name, age))

(a) Formatting Numbers with %

pi = 3.1415926535
print("Pi: %.2f" % pi)  # Pi: 3.14

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4. Raw Strings (r"") – Avoiding Escape Sequences

Raw strings treat backslashes (\) as literal characters.

# Without raw string
print("C:\new\folder")  # Incorrect: \n is treated as a newline

# Using raw string
print(r"C:\new\folder")  # Correct output

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5. Multi-line Strings (''' or """)

Used for large text blocks.

text = """This is
a multi-line
string."""
print(text)

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6. Escape Characters

print("Newline:\nNext line")  # \n - Newline
print("Tab:\tSpace")  # \t - Tab space
print("Backslash: \\")  # \\ - Backslash
print("Quotes: \"Double\" 'Single'")  # \" and \' for quotes

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7. Aligning and Padding Text

name = "Gaurav"
print(f"Left:  |{name:<10}|")  # Left align
print(f"Right: |{name:>10}|")  # Right align
print(f"Center:|{name:^10}|")  # Center align

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8. Formatting Dates & Times in Strings

from datetime import datetime
now = datetime.now()
print(f"Today: {now:%Y-%m-%d}, Time: {now:%H:%M:%S}")

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Conclusion

Method	Python Version	Features	Speed
f-strings	3.6+	Fastest, cleanest, supports expressions	⭐⭐⭐⭐⭐
.format()	2.7+	Flexible but verbose	⭐⭐⭐
% formatting	All	C-style, outdated	⭐⭐

✅ Use f-strings (f"...") whenever possible! 🚀