Python String Formatting

Note: This post is based on my old programming study notes when I taught myself.

String Formatting

After understanding data types in Python, it is important to know how to format them properly.

Method 1: Old formatting using %

• %d: integer
• %s: string
• %f: float
• %c: character

number = 3
day = "several"
y = 'I ate %d apples. So I was happy for %s days.' % (number, day)
print(y)
# Output: I ate 3 apples. So I was happy for several days.

Method 2: Using {} with .format()

Case 1: Direct way

x = "I like {} very much".format('coding')
print(x)
# Output: I like coding very much

Case 2: Using variables inside string

x = 'I like {name} very much'.format(name="Python")
print(x)
# Output: I like Python very much

Advanced .format() usage:

# Multiple variables
text = "My name is {name} and I am {age} years old".format(name="Alice", age=25)

# Positional arguments
text = "The {0} is {1} years old".format("cat", 5)

# Number formatting
price = 49.95
text = "The price is {:.2f}".format(price)  # Output: The price is 49.95

Method 3: Using f-strings (Python 3.6+)

name = 'Elon Musk'
age = 52

z = f"This is {name}."
print(z)
# Output: This is Elon Musk.

# More examples
greeting = f"Hello, {name}! You are {age} years old."
calculation = f"2 + 3 = {2 + 3}"
formatted_number = f"Pi is approximately {3.14159:.2f}"

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Escape Characters

Escape characters allow you to include special characters in strings that would otherwise be difficult to represent.

Common Escape Characters

• Double quote: \"
• Single quote: \'
• Backslash: \\
• Newline: \n
• Tab: \t
• Carriage return: \r

Examples

# Including quotes in strings
text1 = "He said, \"Hello World!\""
text2 = 'It\'s a beautiful day'

# Backslash in path
path = "C:\\Users\\Documents\\file.txt"

# Multi-line strings with newline
message = "First line\nSecond line\nThird line"

# Tab spacing
table = "Name\tAge\tCity"

Raw Strings

Use raw strings (prefix with r) to avoid interpreting escape characters:

# Regular string with escape characters
path1 = "C:\\Users\\Documents"

# Raw string - backslashes are treated literally
path2 = r"C:\Users\Documents"

# Both produce the same result but raw strings are cleaner for paths

Quick Reference

Method	Syntax	Example	Best Use Case
% formatting	"text %s" % value	"Hello %s" % name	Legacy code
.format()	"text {}".format(value)	"Hello {}".format(name)	Python 2.7+ compatibility
f-strings	f"text {value}"	f"Hello {name}"	Modern Python (3.6+) - Recommended

Recommendation: Use f-strings for new code as they are more readable, faster, and less error-prone.

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