Python Strings: Complete Guide with Examples

Quick answer: Learn Python string basics including indexing, slicing, common string methods, f-strings, and immutability, with practical examples.

What is a String?

A string is an ordered, immutable sequence of characters, created using single, double or triple quotes.

name = 'Fireblaze'
course = "Data Science"
description = '''A multi-line
string spanning
several lines'''

Indexing and Slicing

text = "Data Science"

print(text[0])      # D
print(text[-1])      # e
print(text[0:4])     # Data
print(text[::-1])    # ecneicS ataD, reversed

Strings are Immutable

text = "Hello"
text[0] = "J"   # TypeError: 'str' object does not support item assignment

text = "Jello"  # this creates a NEW string, it does not modify the old one

Common String Methods

text = "  Data Science  "

print(text.strip())        # "Data Science", removes leading/trailing whitespace
print(text.upper())        # "  DATA SCIENCE  "
print(text.lower())        # "  data science  "
print(text.strip().replace("Data", "AI"))   # "AI Science"
print(text.strip().split(" "))              # ['Data', 'Science']

Checking String Content

email = "student@fireblaze.in"

print(email.startswith("student"))   # True
print(email.endswith(".in"))          # True
print("@" in email)                   # True
print(email.isdigit())                # False

F-Strings for Formatting

F-strings, introduced in Python 3.6, are the modern, readable way to embed variables directly inside a string.

name = "Priya"
score = 87.456

print(f"{name} scored {score:.1f}%")   # Priya scored 87.5%

Joining and Splitting

words = ['Data', 'Science', 'Course']
sentence = " ".join(words)   # "Data Science Course"

parts = sentence.split(" ")  # ['Data', 'Science', 'Course']

Common Interview Questions

Why are strings immutable in Python?

Immutability makes strings safe to share across a program without risk of unexpected modification, and allows them to be used as dictionary keys since their value cannot change.

What is the difference between str.strip() and str.replace()?

strip() removes leading and trailing whitespace by default, or specified characters if given an argument. replace() substitutes every occurrence of a specified substring with another string, anywhere in the string.

What is the advantage of f-strings over older string formatting methods?

F-strings are more concise and readable, and allow direct embedding of expressions inside the string itself, evaluated at runtime.