Strings — The Full Picture

The idea!

You've covered a lot. Variables, strings, methods, input, output.

This is your reference. Everything in one place.

Come back here whenever you need a reminder.

What is a String

A string is text. Any sequence of characters wrapped in quotes.

name = "Bull"
empty = ""
phrase = "Hello, world!"

Strings can be combined with +:

print("Red" + "Horn")   # RedHorn
print("Red" + " " + "Horn")   # Red Horn

Indexing

Every character has a position. Indexing starts at 0.

name = "Bull"
#       B u l l
#       0 1 2 3

print(name[0])    # B
print(name[-1])   # l — last character

Slicing

Extract a range of characters with [start:stop]. Start included, stop not.

name = "RedHorn"

print(name[0:3])   # Red
print(name[3:])    # Horn
print(name[:3])    # Red
print(name[-4:])   # Horn

Methods — Transform

name = "  Bull  "

print(len("Bull"))          # 4
print(name.strip())         # Bull
print(name.strip().upper()) # BULL
print(name.strip().lower()) # bull
print("bull horn".replace("horn", "red"))  # bull red

Methods — Search & Structure

message = "Hello Bull"

print("Bull" in message)        # True
print(message.find("Bull"))     # 6
print(message.count("l"))       # 3
print(message.startswith("Hello"))  # True
print(message.endswith("Bull"))     # True
print(message.split())          # ['Hello', 'Bull']

Print Formatting

name = "Bull"
age = 25

# f-strings
print(f"My name is {name} and I am {age} years old.")

# sep and end
print("Red", "Horn", sep="-")   # Red-Horn
print("Hello", end=" ")
print("Bull")                    # Hello Bull

# Number formatting
price = 3.14159
print(f"Price: {price:.2f}")    # Price: 3.14

Input

# input() always returns a string
name = input("Enter your name: ")

# Convert if you need a number
age = int(input("Enter your age: "))
height = float(input("Enter your height: "))

print(f"Hi {name}, you are {age} years old.")

Common Mistakes

• Quotes must match — open and close with the same type
• Indexing starts at 0, not 1
• Going beyond the last index → IndexError
• Methods return a new string — reassign to keep the change
• Can't add a string and a number — use str() or an f-string
• Strings are case sensitive — "Bull" and "bull" are not the same

What you should understand now

• Strings are text — and text is data
• Every character has a position
• Methods transform, search, and structure strings
• f-strings are the cleanest way to format output
• input() always returns a string — convert when needed