Day 14: Strings — How Programs Read and Use Text!

What's a String?

Every message you send on WhatsApp, every search you type on Google, every username on Instagram — all of that is text. In Python, text is called a String. Think of it like a train of letters — "Rohith" is 6 carriages: R, o, h, i, t, h!

Creating a String

name = "Rohith"
message = "Hello World"
city = "Hyderabad"

Always use quotes. Single or double both work. Without quotes Python thinks it's a variable name, not text!

Strings Are Like Lists of Letters

Just like lists, each letter in a string has a position starting from 0!

name = "Rohith"

print(name[0])   # R
print(name[1])   # o
print(name[5])   # h

R is at position 0, o is at 1, h is at 2, i is at 3, t is at 4, h is at 5. Counting always starts from zero!

Useful String Tricks

name = "rohith"

print(len(name))
print(name.upper())
print(name.lower())
print(name.capitalize())

Instagram uses upper() and lower() to make username searches work whether you type "PRIYA" or "priya". Same result!

Joining Strings Together

first = "Rohith"
last = "Builds"

full = first + " " + last
print(full)

Output: Rohith Builds. The + joins strings together. This is called concatenation. WhatsApp uses this to show "Priya is typing..." by joining a name with " is typing..."!

Common Mistakes

Mistake 1 — Forgetting quotes.

name = Rohith
name = "Rohith"

Mistake 2 — Going out of range.

name = "Rohith"
print(name[6])
print(name[5])

Mini Challenge

Quick Quiz

Q: What position is the first letter of any string? A: Position 0 — always start counting from zero!

Q: How do you find how many characters are in a string? A: len(string)!

Q: How do you join two strings together? A: Use the + sign — "Hello" + " " + "World"!

Key Takeaways