String manipulation

Working with text

Now that you know what strings are, let’s learn how to manipulate them. Python gives you powerful tools to work with text.

String operations & Formatting

Concatenation & Repetition

You can join strings together using + or repeat them using *:

first_name = "Aarav"
last_name = "Sharma"

# Concatenation
full_name = first_name + " " + last_name  # "Aarav Sharma"

# Repetition
star = "*"
stars = star * 10  # "**********"
separator = "-" * 20  # "--------------------"

String Formatting

Python provides multiple ways to format strings. While f-strings are the modern standard, you will also see the older .format() method in older codebases.

name = "Amit"
age = 25
role = "Developer"

# 1. Using f-strings (modern Python way!)
intro1 = f"I'm {name} and I'm {age} years old."

# 2. Using .format() with positional arguments
intro2 = "Hello, {} is a {}.".format(name, role)

# 3. Using .format() with named arguments
intro3 = "Hello, {user} is a {job}.".format(user=name, job=role)

String Indexing & Slicing

Indexing

Every character in a string has a number representing its position, called an index. Indexes start at 0 for the first character. You can also count backward from the end using negative indexes (starting at -1).

text = "Python"

# Positive indexing (left to right)
print(text[0])   # 'P'
print(text[2])   # 't'

# Negative indexing (right to left)
print(text[-1])  # 'n' (last character)
print(text[-3])  # 'h'

Accessing an index that doesn’t exist (e.g., text[10]) raises an IndexError.

Slicing

Slicing lets you extract a section of a string using the syntax [start:stop:step]. The character at start is included, but the character at stop is excluded.

text = "Python Programming"

# Basic slicing
print(text[0:6])   # "Python" (indexes 0 to 5)
print(text[7:14])  # "Program"

# Omitting start or stop (defaults to start/end of string)
print(text[:6])    # "Python"
print(text[7:])    # "Programming"
print(text[:])     # "Python Programming" (copies the string)

# Step values (skips characters)
print(text[0:6:2]) # "Pto" (every 2nd character from index 0 to 5)

# Negative steps (reversing a string)
print(text[::-1])  # "gnimmargorP nohtyP" (reverses the whole string)
print(text[5:1:-1])# "noht" (steps backward from index 5 to 2)

Advanced Slicing (Mixed Boundaries & Steps)

You can mix positive/negative indexes and positive/negative steps together:

text = "Python Programming"

# 1. Mixed positive & negative index boundaries
print(text[1:-2])    # "ython Programmin" (starts at index 1, stops before index -2)
print(text[-11:15])  # "Program" (starts at index -11, stops before index 15)

# 2. Mixed values in step direction
print(text[1:-1:2])  # "yhnPoga mn" (every second character from index 1 to the end)
print(text[-2:2:-3]) # "mrgPnt" (steps backward by 3 starting at index -2 down to index 3)

Slicing Edge Cases

Slicing is very forgiving compared to indexing:

text = "Python"

# 1. Out-of-bounds slicing does NOT raise an error
print(text[0:100]) # "Python" (just returns the available string)

# 2. Conflicting direction produces an empty string
print(text[5:2])   # "" (starts at 5, goes forward, but 2 is behind it)

String methods

Python strings come with many built-in methods - functions you can call directly on any string. These methods let you transform text, search for patterns, and clean up data. The best part? You can often guess what they do from their names - upper() makes text uppercase, replace() replaces text, and so on.

Changing case

text = "Python Programming"

print(text.lower())      # "python programming"
print(text.upper())      # "PYTHON PROGRAMMING"
print(text.title())      # "Python Programming"

Cleaning strings

messy = "  hello world  "
print(messy.strip())     # "hello world" (removes whitespace)

price = "₹19.99"
print(price.strip("₹"))  # "19.99"

Finding and replacing

message = "I love Python programming with Python"

# Check if something exists
print("Python" in message)        # True
print(message.startswith("I"))   # True
print(message.endswith("Python")) # True

# Find position
print(message.find("Python"))     # 7 (first occurrence)
print(message.count("Python"))    # 2 (number of times)

# Replace
new_message = message.replace("Python", "JavaScript")
print(new_message)  # "I love JavaScript programming with JavaScript"

Splitting and Joining

You can split a string into a list of strings, and join a list of strings back together.

# Splitting strings
data = "apple,banana,cherry"
fruits = data.split(",")
print(fruits)  # ['apple', 'banana', 'cherry']

# Joining strings
joined_data = " | ".join(fruits)
print(joined_data)  # "apple | banana | cherry"

Python has over 40 string methods! We’ve covered the most common ones here. For a complete list, check the official Python documentation.

Common mistakes

Forgetting the f in f-strings

# Wrong
name = "Alice"
message = "Hello {name}"  # Prints: "Hello {name}"

# Right
message = f"Hello {name}"  # Prints: "Hello Alice"

Wrong quotes in strings

# Wrong - mismatched quotes
text = 'It's Python'

# Right - escape or use different quotes
text = "It's Python"  # Double quotes outside
text = 'It\'s Python'  # Escape the apostrophe

Practice & Exercises

To reinforce what you’ve learned in this section (Concatenation, Repetition, and String Methods), practice with these interactive notebooks:

Follow-Along Practice

Practice f-strings, repetitions, case transformations, stripping whitespace, and replacing text.💻 VS Code | 🚀 Colab | 📥 Download

Practice Exercises

Test your knowledge with hands-on exercises on custom greetings, cleaning email addresses, and replacement logic.💻 VS Code | 🚀 Colab | 📥 Download

What’s next?

You’ve mastered working with data! Ready to make your programs smart with decision-making?

Control flow

Learn if statements and loops

Getting started

Data types

Working with data

Control flow

Data structures

Packing & Unpacking

Working with text

String operations & Formatting

Concatenation & Repetition

String Formatting

String Indexing & Slicing

Indexing

Slicing

Advanced Slicing (Mixed Boundaries & Steps)

Slicing Edge Cases

String methods

Changing case

Cleaning strings

Finding and replacing

Splitting and Joining

Common mistakes

Practice & Exercises

Follow-Along Practice

Practice Exercises

What’s next?

Control flow

​Working with text

​String operations & Formatting

​Concatenation & Repetition

​String Formatting

​String Indexing & Slicing

​Indexing

​Slicing

​Advanced Slicing (Mixed Boundaries & Steps)

​Slicing Edge Cases

​String methods

​Changing case

​Cleaning strings

​Finding and replacing

​Splitting and Joining

​Common mistakes

​Practice & Exercises

Follow-Along Practice

Practice Exercises

​What’s next?

Control flow

Working with text

String operations & Formatting

Concatenation & Repetition

String Formatting

String Indexing & Slicing

Indexing

Slicing

Advanced Slicing (Mixed Boundaries & Steps)

Slicing Edge Cases

String methods

Changing case

Cleaning strings

Finding and replacing

Splitting and Joining

Common mistakes

Practice & Exercises

What’s next?