Strings in Python

In Python, strings are one of the most commonly used data types. They are used to store and manipulate textual data, such as names, messages, or any sequence of characters. Python strings are powerful, immutable, and come with a rich set of built-in methods.

What is a String?

A string in Python is a sequence of Unicode characters enclosed in single quotes ('...'), double quotes ("..."), or triple quotes ('''...''' or """...""").

Syntax:

string_syntax.py

single = 'Hello'
double = "World"
multiline = """This is
a multi-line string."""

String Characteristics

Immutable: Once created, strings cannot be modified.
Indexed: Each character has a position (starting from 0).
Iterable: Strings can be looped over.
Supports Slicing: You can extract substrings.

Example 1: Basic String Operations

string_basic_ops.py

greeting = "Hello"
name = "Alice"
message = greeting + ", " + name + "!"
print(message)

This demonstrates concatenation of multiple strings to form a complete message. The + operator joins strings.

Example 2: Indexing and Slicing

string_index_slice.py

word = "Python"
print(word[0])      # First character
print(word[-1])     # Last character
print(word[1:4])    # Characters from index 1 to 3

word[0] accesses the first character.
word[-1] accesses the last character using negative indexing.
word[1:4] slices from index 1 up to (but not including) index 4.

Example 3: String Methods

string_methods.py

text = "  Learn Python Programming  "
print(text.strip())       # Removes leading/trailing whitespace
print(text.lower())       # Converts to lowercase
print(text.upper())       # Converts to uppercase
print(text.replace("Python", "Java"))  # Replaces substring

Python provides many string methods for transforming and cleaning text.

Example 4: Multiline Strings and Escaping

string_multiline.py

message = """Hello,
This is a multiline
string with line breaks."""
print(message)
 
escaped = "He said, \"Python is awesome!\""
print(escaped)

Triple quotes allow multiline string literals.
Backslashes (\) are used to escape special characters like \", \n, \t.

Example 5: String Formatting

Python supports multiple string formatting methods:

Using `f-strings` (Recommended in Python 3.6+)

string_fstring.py

name = "Alice"
print(f"Welcome, {name}!")

Using `.format()` method

string_format.py

print("Welcome, {}!".format("Alice"))

Using `%` formatting (older style)

string_percent.py

print("Welcome, %s!" % "Alice")

Example 6: Iterating Over a String

string_iteration.py

language = "Python"
for char in language:
    print(char)

Each character in a string can be accessed using a for loop because strings are iterable.

Commonly Used String Methods

Method	Description
`str.lower()`	Converts string to lowercase
`str.upper()`	Converts string to uppercase
`str.strip()`	Removes whitespace from both ends
`str.replace()`	Replaces a substring with another
`str.split()`	Splits string into a list by separator
`str.join()`	Joins elements of an iterable with string
`str.startswith()`	Checks if string starts with a prefix
`str.endswith()`	Checks if string ends with a suffix

String Immutability

Strings are immutable, meaning operations return new strings and do not alter the original.

string_immutable.py

name = "Alice"
new_name = name.replace("A", "E")
print(name)       # Alice
print(new_name)   # Elice

name remains unchanged. A new string is returned.

Summary

Strings in Python are immutable sequences of characters.
They support indexing, slicing, iteration, and a rich set of methods.
Triple quotes allow for multiline strings.
Formatting can be done using f-strings, .format(), or %.

In the next article, we’ll explore Lists in Python — dynamic arrays that support mutable operations and heterogeneous data.

Numeric Data type Lists