Strings in Python

Quotes: Single, Double, and Triple

A string in Python can be enclosed in single ('), double ("), or triple quotes (''' or """). Triple quotes are typically used for multi-line strings.

Example:

x = '''first line
second line
third line'''
print(x)

Output:

first line
second line
third line

Length of Strings

Use the len() function to determine the length of a string.

Example:

x = 'good'
print(len(x))  # Output: 4

Operations on Strings

1. Concatenation: Using the + operator.

string1 = 'first'
string2 = ','
string3 = 'second'
result = string1 + string2 + string3
print(result)  # Output: first,second

1. Replication: Using the * operator to repeat a string.

s = 'good'
print(s * 5)  # Output: goodgoodgoodgoodgood

1. Comparison: Using ==, >, < operators for lexicographic comparisons.

print('good' > 'bad')  # Output: True

Escape Characters

The backslash (\) is used to introduce special characters.

• \n for newline
• \t for tab
• \' for escaping single quotes

Example:

print('This is the first line.\nThis is the second line.')

Output:

This is the first line.
This is the second line.

Substrings

The in keyword checks if a string is a substring of another.

Example:

a = 'good'
b = 'very good'
print(a in b)  # Output: True

Indexing and Slicing

Strings support both positive and negative indexing. The first character has index 0, and the last has index -1.

Example:

word = 'world'
print(word[0])   # Output: w
print(word[-1])  # Output: d

Slicing: To extract a portion of a string.

email = 'CS_10_014@iitm.ac.in'
roll = email[6:9]  # Output: 014

Immutability of Strings

Strings are immutable in Python, meaning their contents cannot be changed once created.

Example:

word = 'hello'
word[0] = 'H'  # This will raise an error

String Methods

• capitalize(): Capitalizes the first letter.
• isalpha(): Checks if all characters are alphabetic.

Example:

sentence = 'hello world'
print(sentence.capitalize())  # Output: Hello world

name = 'John'
print(name.isalpha())  # Output: True