Strings & Text Operations

Working with Strings

Strings are sequences of characters. Python gives you powerful tools to manipulate text.

String Concatenation (Joining)

Combine strings with the + operator:

first = "John"
last = "Smith"
full_name = first + " " + last    # "John Smith"

F-Strings (Modern Python)

The easiest way to embed variables in text:

name = "Alice"
age = 28
score = 95.5

# F-string (readable and powerful!)
print(f"Hello {name}!")              # Hello Alice!
print(f"{name} is {age} years old")  # Alice is 28 years old
print(f"Score: {score:.1f}%")        # Score: 95.5%

String Formatting Examples

price = 19.995

f"{price}"        # "19.995"
f"{price:.2f}"    # "19.99"   ← 2 decimals

count = 5000
f"{count:,}"      # "5,000"   ← with commas

text = "hello"
f"{text.upper()}" # "HELLO"   ← call methods inside!

Essential String Methods

Making changes (note: strings are immutable—these return NEW strings):

text = "  Hello World  "

text.lower()           # "  hello world  "
text.upper()           # "  HELLO WORLD  "
text.strip()           # "Hello World"      ← removes whitespace
text.replace("World", "Python")  # "  Hello Python  "

Checking content:

text = "Hello"

"H" in text         # True (substring check)
text.startswith("He")  # True
text.endswith("lo")    # True
text.isdigit()      # False

"  123  ".isdigit() # False (has spaces!)
"123".isdigit()     # True

Finding and splitting:

sentence = "I love Python programming"

sentence.find("Python")    # 7 (position)
sentence.count("o")        # 3 (occurrences)
sentence.split()           # ["I", "love", "Python", "programming"]
sentence.split(" ")        # same result

Important: String methods don't modify the original string—they return a new one. Strings are immutable!