How to Manipulate Strings in Python

Strings are one of the most commonly used data types in Python. Here’s how to work with them effectively.

Creating Strings

# Single or double quotes
single = 'Hello'
double = "World"

# Multi-line strings
multi = """This is a
multi-line string"""

# Raw strings (ignore escape characters)
raw = r"C:\Users\name\Documents"
print(raw)  # C:\Users\name\Documents

String Indexing and Slicing

text = "Hello, World!"

# Indexing (0-based)
print(text[0])   # H
print(text[-1])  # !

# Slicing [start:end:step]
print(text[0:5])   # Hello
print(text[7:])    # World!
print(text[:5])    # Hello
print(text[::2])   # Hlo ol!
print(text[::-1])  # !dlroW ,olleH (reversed)

Common String Methods

Case Conversion

text = "Hello, World!"

print(text.upper())      # HELLO, WORLD!
print(text.lower())      # hello, world!
print(text.title())      # Hello, World!
print(text.capitalize()) # Hello, world!
print(text.swapcase())   # hELLO, wORLD!

Searching and Checking

text = "Hello, World!"

# Find substring position
print(text.find("World"))    # 7
print(text.find("Python"))   # -1 (not found)
print(text.index("World"))   # 7 (raises error if not found)

# Check content
print(text.startswith("Hello"))  # True
print(text.endswith("!"))        # True
print("World" in text)           # True

# Character type checks
print("hello".isalpha())    # True
print("123".isdigit())      # True
print("hello123".isalnum()) # True
print("   ".isspace())      # True

Modifying Strings

text = "  Hello, World!  "

# Remove whitespace
print(text.strip())   # "Hello, World!"
print(text.lstrip())  # "Hello, World!  "
print(text.rstrip())  # "  Hello, World!"

# Replace
print(text.replace("World", "Python"))  # "  Hello, Python!  "

# Split and Join
words = "apple,banana,cherry".split(",")
print(words)  # ['apple', 'banana', 'cherry']

joined = "-".join(words)
print(joined)  # apple-banana-cherry

String Formatting

f-strings (Recommended)

name = "Alice"
age = 30

# Basic formatting
print(f"Name: {name}, Age: {age}")

# Expressions
print(f"Next year: {age + 1}")

# Formatting numbers
price = 49.99
print(f"Price: ${price:.2f}")  # Price: $49.99

pi = 3.14159
print(f"Pi: {pi:.3f}")  # Pi: 3.142

# Padding and alignment
print(f"{'left':<10}|{'center':^10}|{'right':>10}")
# left      |  center  |     right

format() Method

# Positional arguments
print("{} and {}".format("Alice", "Bob"))  # Alice and Bob

# Named arguments
print("{name} is {age}".format(name="Alice", age=30))

# Number formatting
print("{:.2f}".format(3.14159))  # 3.14
print("{:,}".format(1000000))    # 1,000,000

String Operations

# Concatenation
greeting = "Hello" + " " + "World"
print(greeting)  # Hello World

# Repetition
echo = "Ha" * 3
print(echo)  # HaHaHa

# Length
print(len("Hello"))  # 5

# Count occurrences
text = "banana"
print(text.count("a"))  # 3

Working with Characters

# Convert to list of characters
text = "Hello"
chars = list(text)
print(chars)  # ['H', 'e', 'l', 'l', 'o']

# Iterate through characters
for char in "Hello":
    print(char, ord(char))  # Character and ASCII code

# Character from code
print(chr(65))  # A
print(chr(97))  # a

Practical Examples

# Clean and normalize input
user_input = "  JOHN DOE  "
clean_name = user_input.strip().title()
print(clean_name)  # John Doe

# Extract file extension
filename = "document.pdf"
extension = filename.split(".")[-1]
print(extension)  # pdf

# Check valid email (simple)
email = "user@example.com"
is_valid = "@" in email and "." in email
print(is_valid)  # True

# Create slug from title
title = "How to Use Python Strings!"
slug = title.lower().replace(" ", "-").replace("!", "")
print(slug)  # how-to-use-python-strings

Summary

• Use indexing [i] and slicing [start:end:step] to access parts
• Use .upper(), .lower(), .title() for case conversion
• Use .strip(), .replace(), .split(), .join() for modification
• Use f-strings for formatting: f"Value: {variable}"
• Strings are immutable - methods return new strings