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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