Interview Bite

Introduction

Python provides a rich set of built-in string methods that make it easy to manipulate and process text data. These methods allow you to perform various operations such as searching, replacing, splitting, joining, and more. This guide will explore the most commonly used string methods with practical examples.

Commonly Used String Methods

1. lower() and upper()

These methods convert a string to lowercase or uppercase.

# Example
text = "Hello World!"
print(text.lower())  # Output: hello world!
print(text.upper())  # Output: HELLO WORLD!

2. strip(), lstrip(), and rstrip()

These methods remove whitespace (or specified characters) from the beginning, end, or both sides of a string.

# Example
text = "   Hello World!   "
print(text.strip())   # Output: "Hello World!"
print(text.lstrip())  # Output: "Hello World!   "
print(text.rstrip())  # Output: "   Hello World!"

3. replace()

Replaces occurrences of a substring with another substring.

# Example
text = "I love Python. Python is awesome!"
print(text.replace("Python", "programming"))
# Output: I love programming. programming is awesome!

4. split() and join()

The split() method splits a string into a list, while join() combines a list of strings into a single string.

# Example
text = "Python,Java,C++"
languages = text.split(",")
print(languages)  # Output: ['Python', 'Java', 'C++']

joined_text = " | ".join(languages)
print(joined_text)  # Output: Python | Java | C++

5. find() and index()

These methods return the position of a substring. find() returns -1 if the substring is not found, while index() raises a ValueError.

# Example
text = "Python is fun!"
print(text.find("fun"))  # Output: 10
print(text.index("fun")) # Output: 10

6. startswith() and endswith()

These methods check if a string starts or ends with a specific substring.

# Example
text = "Python programming"
print(text.startswith("Python"))  # Output: True
print(text.endswith("programming"))  # Output: True

7. isdigit(), isalpha(), and isalnum()

These methods check if a string is numeric, alphabetic, or alphanumeric.

# Example
text = "12345"
print(text.isdigit())  # Output: True
print(text.isalpha())  # Output: False
text2 = "Python123"
print(text2.isalnum())  # Output: True

8. capitalize(), title(), and swapcase()

These methods modify the case of characters in a string.

# Example
text = "hello world"
print(text.capitalize())  # Output: Hello world
print(text.title())       # Output: Hello World
print(text.swapcase())    # Output: HELLO WORLD

Interview Questions

• Question 1: What is the difference between find() and index() methods?
• Question 2: How would you split a string into a list of words?
• Question 3: Write a Python program to count the occurrences of a specific character in a string.
• Question 4: How can you check if a string contains only numeric characters?
• Question 5: Demonstrate the use of strip() with a custom character set.

Conclusion

Python string methods are powerful tools for text processing and manipulation. By mastering these methods, you can efficiently handle various text-based tasks. Whether you are cleaning data, building user interfaces, or parsing logs, these methods will come in handy.