Comprehensive Guide to Python Strings

Introduction

In Python, a string is an immutable sequence data type. It represents a sequence of Unicode characters, which can be enclosed in single, double, or triple quotes.

String Literals in Python

The following examples show valid string literals in Python:

'This is a string in Python'  # Single quotes
"This is a string in Python"  # Double quotes
'''This is a string in Python'''  # Triple single quotes
"""This is a string in Python"""  # Triple double quotes

Assigning Strings to Variables

String literals can be assigned to variables:

str1 = 'This is a string in Python'
print(str1)
str2 = "This is a string in Python"
print(str2)

Output:

This is a string in Python
This is a string in Python

Multi-line Strings

Multi-line strings must be enclosed in triple quotes:

str1 = '''This is
the first
Multi-line string.'''
print(str1)

str2 = """This is
the second
Multi-line
string."""
print(str2)

Output:

This is
the first
Multi-line string.

This is
the second
Multi-line
string.

Embedding Quotes in Strings

You can embed quotes within strings by using different enclosing quotes:

str1 = 'Welcome to "Python Tutorial" on TutorialsTeacher'
print(str1)

str2 = "Welcome to 'Python Tutorial' on TutorialsTeacher"
print(str2)

Output:

Welcome to "Python Tutorial" on TutorialsTeacher
Welcome to 'Python Tutorial' on TutorialsTeacher

String Length

Use the len() function to find the length of a string:

greet = 'Hello'
print(len(greet))  # Output: 5

String Indexing

Strings are ordered collections of characters and can be indexed:

greet = 'hello'
print(greet[0])  # Output: 'h'
print(greet[1])  # Output: 'e'
print(greet[4])  # Output: 'o'

Negative indexing is also supported:

greet = 'hello'
print(greet[-1])  # Output: 'o'

Immutability of Strings

Strings in Python are immutable, meaning they cannot be modified.

greet = 'hello'
greet[0] = 'A'  # This will throw an error

The 'str' Class

All strings are objects of the str class:

greet = 'hello'
print(type(greet))  # Output: <class 'str'>

Use the str() function to convert numbers to strings:

print(str(100))  # Output: '100'
print(str(True))  # Output: 'True'

Escape Sequences

Escape sequences allow special characters to be included in strings:

str1 = 'Welcome to \'Python Tutorial\' on TutorialsTeacher'
print(str1)

str2 = "Welcome to \"Python Tutorial\" on TutorialsTeacher"
print(str2)

Output:

Welcome to 'Python Tutorial' on TutorialsTeacher
Welcome to "Python Tutorial" on TutorialsTeacher

To ignore escape sequences, prefix the string with an r or R:

str1 = r'Welcome to \'Python Tutorial\' on TutorialsTeacher'
print(str1)

Common Escape Sequences

• \\ Backslash
• \b Backspace
• \n Newline
• \t Tab
• \xnn Hexadecimal notation

Python String Operations

Python supports several operations on strings:

a = 'hello'
b = 'world'
# Concatenation
a_b = a + b  # Output: 'helloworld'

# Repetition
a_3 = a * 3  # Output: 'hellohellohello'

# Indexing
t = a[2]  # Output: 'l'

# Slicing
py = a[0:2]  # Output: 'he'

# Membership
is_y_in_a = 'y' in a  # Output: True
is_x_in_a = 'x' not in a  # Output: True

Explore these string functionalities to master Python's handling of text data.