Welcome to Day 5 of the 100 Days of Python series!
Today we’re diving deep into one of the most commonly used data types in Python: strings.
Whether you’re building a chatbot, scraping websites, or working with data — you'll be using strings all the time. So let’s master the basics and learn how to format and manipulate strings effectively.
📦 What You'll Learn Today
- What strings are and how to define them
- String indexing and slicing
- Common string methods
- String concatenation and repetition
- How to format strings cleanly
🔤 What Is a String?
In Python, a string is a sequence of characters surrounded by quotes.
name = "Alice" greeting = 'Hello, world!' You can use either single (' ') or double (" ") quotes.
🧱 String Indexing and Slicing
Indexing:
Each character in a string has an index number:
word = "Python" print(word[0]) # P print(word[5]) # n Python uses zero-based indexing, so the first character is at position 0.
Slicing:
You can extract parts of strings using slicing:
print(word[0:3]) # Pyt print(word[2:]) # thon print(word[-1]) # n (last character) 🔁 String Concatenation and Repetition
Concatenation:
Use + to join strings:
first = "Good" second = "Morning" print(first + " " + second) # Good Morning Repetition:
Use * to repeat a string:
print("Ha" * 3) # HaHaHa 🧽 Common String Methods
Python strings come with lots of built-in methods:
text = " Hello, Python! " print(text.strip()) # Remove whitespace: "Hello, Python!" print(text.lower()) # Convert to lowercase print(text.upper()) # Convert to uppercase print(text.replace("Python", "World")) # Replace text print(text.find("Python")) # Find substring index Some Useful String Methods:
| Method | Description |
|---|---|
.strip() | Removes leading/trailing whitespace |
.lower() | Converts to lowercase |
.upper() | Converts to uppercase |
.replace() | Replaces one substring with another |
.find() | Finds the first index of a substring |
.split() | Splits string into a list |
.join() | Joins list into a string |
🧠 String Formatting
Let’s say you want to include variables in a sentence. Here are 3 ways to format strings:
1️⃣ Concatenation (not ideal):
name = "Alice" print("Hello " + name + "!") 2️⃣ str.format():
print("Hello, {}!".format(name)) 3️⃣ f-Strings (Best Practice in Python 3.6+):
print(f"Hello, {name}!") f-strings are readable, fast, and the most modern way to format strings.
You can even do expressions inside them:
age = 25 print(f"In 5 years, you’ll be {age + 5} years old.") 📌 Bonus: Multiline Strings
Use triple quotes for multiline strings:
message = """Hello, This is a multi-line string in Python.""" print(message) 🚀 Recap
Today you learned:
- How to define, access, and slice strings
- How to join and repeat strings
- Common string methods
- Best practices for string formatting using f-strings
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