Strings

Strings are sequences of characters enclosed in quotes. They are one of the most commonly used data types in Python, allowing you to work with text.

Creating Strings

  1. Single Quotes: 
    single_quote = 'Hello, World!'
  2. Double Quotes: 
    double_quote = "Hello, Python!"
  3. Triple Quotes: Used for multi-line strings or docstrings: 
    multi_line = """This is
a multi-line
string."""

Common String Operations

Operation Example Result
Concatenation 'Hello' + ' World' 'Hello World'
Repetition 'Python' * 3 'PythonPythonPython'
Length len('Python') 6
Access by Index 'Python'[0] 'P'
Slicing 'Python'[0:3] 'Pyt'
Check Substring 'Py' in 'Python' True

Examples:

greeting = "Hello"
name = "Alice"

# Concatenation
print(greeting + " " + name)  # Hello Alice

# Repetition
print(name * 3)  # AliceAliceAlice

# Length
print(len(greeting))  # 5

# Access by Index
print(greeting[1])  # e

# Slicing
print(greeting[1:4])  # ell

# Check Substring
print("lo" in greeting)  # True

String Methods

Python provides several built-in methods to work with strings:

Method Description Example Result
lower() Converts to lowercase 'PYTHON'.lower() 'python'
upper() Converts to uppercase 'python'.upper() 'PYTHON'
strip() Removes whitespace ' hello '.strip() 'hello'
replace(a, b) Replaces substring a with b 'hello'.replace('e', 'a') 'hallo'
split(delim) Splits string into a list 'a,b,c'.split(',') ['a', 'b', 'c']
join(iterable) Joins elements with a delimiter ','.join(['a', 'b', 'c']) 'a,b,c'

Examples:

text = "  Python is Fun!  "

# Convert to lowercase
print(text.lower())  # python is fun!

# Convert to uppercase
print(text.upper())  # PYTHON IS FUN!

# Remove whitespace
print(text.strip())  # Python is Fun!

# Replace substring
print(text.replace("Fun", "Awesome"))  # Python is Awesome!

# Split and join
words = text.strip().split(" ")  # ['Python', 'is', 'Fun!']
print("-".join(words))  # Python-is-Fun!

Escape Characters

Special characters in strings can be included using backslashes (\):

Escape Character Description Example Result
\' Single quote 'It\'s OK' It's OK
\" Double quote "He said \"Hi\"" He said "Hi"
\\ Backslash 'C:\\path' C:\path
\n Newline 'Hello\nWorld' Hello↵World
\t Tab 'Hello\tWorld' Hello World

Example:

print("It's a beautiful day!")
print("Line1\nLine2")
print("Path: C:\\Users\\Alice")

Practice Exercises

  1. Create a string variable containing your full name.
    • Print the length of the string.
    • Extract your first and last names using slicing.
  2. Take a string "Hello, World!":
    • Convert it to lowercase.
    • Replace "World" with "Python".
    • Split it into a list of words.
  3. Print a multi-line string using triple quotes.

Strings are an essential part of Python and understanding them will help you work with text-based data effectively!

Next Lesson: Slicing and Indexing