Working with Strings in Python

1. Introduction

Strings in Python are immutable sequences of Unicode characters. They are one of the most commonly used data types and provide various functionalities to manipulate text.

2. String Creation

Strings can be created in Python using single quotes, double quotes, or triple quotes for multi-line strings.

single_quote_string = 'Hello, World!'
double_quote_string = "Hello, World!"
triple_quote_string = """This is a
multi-line string."""

3. String Manipulation

Common string manipulation techniques include:

• Concatenation: Combining strings using the + operator.
• Repetition: Repeating strings using the * operator.
• Slicing: Accessing parts of a string using indices.

greeting = "Hello"
name = "Alice"
combined = greeting + " " + name  # "Hello Alice"
repeated = greeting * 3  # "HelloHelloHello"
sub_string = greeting[1:4]  # "ell"

4. Common String Methods

Python provides numerous built-in methods for string manipulation:

• str.lower(): Converts a string to lowercase.
• str.upper(): Converts a string to uppercase.
• str.strip(): Removes leading and trailing whitespace.
• str.replace(old, new): Replaces occurrences of a substring.
• str.split(separator): Splits a string into a list.
• str.join(iterable): Joins elements of an iterable into a string.

text = "   Python is fun!   "
print(text.lower())  # "   python is fun!   "
print(text.strip())  # "Python is fun!"
print(text.replace("fun", "awesome"))  # "   Python is awesome!   "
words = text.split()  # ['Python', 'is', 'fun!']
joined = ", ".join(words)  # "Python, is, fun!"

5. String Formatting

Formatting strings can be done using three primary methods:

• f-strings (Python 3.6+): Embedding expressions inside string literals.
• str.format(): More traditional method of formatting strings.
• Percent formatting: Old-style formatting using % operator.

name = "Alice"
age = 30
# f-strings
print(f"{name} is {age} years old.")

# str.format()
print("{} is {} years old.".format(name, age))

# Percent formatting
print("%s is %d years old." % (name, age))

6. FAQ

text = "Hello, World!"
print("Hello" in text)  # True