Python Strings

Strings are a fundamental data type in Python, used to represent text. Strings in Python are sequences of characters, making them iterable, and are enclosed in either single quotes (`'`), double quotes (`"`), or triple quotes (`'''` or `"""`) for multi-line strings. Strings are immutable, meaning they cannot be changed after creation. This guide covers string creation, indexing, slicing, common methods, formatting, and other useful features in Python.

Creating Strings

# Single-line strings
string1 = 'Hello, World!'
string2 = "Python Strings"

# Multi-line string
multi_line_string = '''This is a
multi-line
string in Python.'''

print(string1)
print(string2)
print(multi_line_string)

Output:
Hello, World!
Python Strings
This is a
multi-line
string in Python.

Accessing Characters in Strings

greeting = "Hello"
print("First character:", greeting[0])   # First character
print("Last character:", greeting[-1])   # Last character

Output:
First character: H
Last character: o

String Slicing

text = "Python Programming"
print("Characters 0 to 5:", text[0:6])  # Slice from index 0 to 5
print("Every second character:", text[::2])  # Slice with step
print("Reverse string:", text[::-1])  # Reverse the string

Output:
Characters 0 to 5: Python
Every second character: Pto rgamn
Reverse string: gnimmargorP nohtyP

String Concatenation and Repetition

str1 = "Hello"
str2 = "World"
concatenated = str1 + " " + str2
repeated = str1 * 3

print("Concatenated string:", concatenated)
print("Repeated string:", repeated)

Output:
Concatenated string: Hello World
Repeated string: HelloHelloHello

Common String Methods

sample_text = "Python Programming"

# Convert to uppercase
print("Uppercase:", sample_text.upper())

# Convert to lowercase
print("Lowercase:", sample_text.lower())

# Find a substring
print("Position of 'Prog':", sample_text.find("Prog"))

# Replace a substring
print("Replace 'Python' with 'Java':", sample_text.replace("Python", "Java"))

Output:
Uppercase: PYTHON PROGRAMMING
Lowercase: python programming
Position of 'Prog': 7
Replace 'Python' with 'Java': Java Programming

String Formatting

name = "Alice"
age = 30

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

# Using format() method
print("My name is {} and I am {} years old.".format(name, age))

# Using % operator
print("My name is %s and I am %d years old." % (name, age))

Output:
My name is Alice and I am 30 years old.
My name is Alice and I am 30 years old.
My name is Alice and I am 30 years old.

Checking for Substrings

text = "Python programming is fun"
print("Contains 'Python':", 'Python' in text)
print("Contains 'Java':", 'Java' in text)

Output:
Contains 'Python': True
Contains 'Java': False

Splitting and Joining Strings

sentence = "Python is great for programming"
words = sentence.split()  # Splits by spaces by default
print("Split into words:", words)

# Joining words with hyphen
joined_sentence = "-".join(words)
print("Joined with hyphen:", joined_sentence)

Output:
Split into words: ['Python', 'is', 'great', 'for', 'programming']
Joined with hyphen: Python-is-great-for-programming

Trimming Strings

text_with_spaces = "   Hello, Python!   "
print("Original:", text_with_spaces)
print("Strip all:", text_with_spaces.strip())
print("Left strip:", text_with_spaces.lstrip())
print("Right strip:", text_with_spaces.rstrip())

Output:
Original: Hello, Python!
Strip all: Hello, Python!
Left strip: Hello, Python!
Right strip: Hello, Python!

Counting Occurrences

text = "Python is fun. Python is easy to learn."
print("Occurrences of 'Python':", text.count("Python"))

Output:
Occurrences of 'Python': 2

String Immutability

original = "Hello"
modified = original.replace("H", "J")
print("Original String:", original)
print("Modified String:", modified)

Output:
Original String: Hello
Modified String: Jello

Summary