Understanding Python Strings and String Exercise

In Python, a string is a sequence of characters enclosed in quotes. Strings are used to handle text, and Python provides several methods to manipulate and operate on these text-based sequences efficiently. Strings in Python are immutable, meaning they cannot be changed after they are created, but various string methods allow us to create modified versions of the original string.

Creating Strings

# Using single or double quotes
string1 = 'Hello'
string2 = "World"

# Multi-line string using triple quotes
multi_line = '''This is a 
multi-line string.'''

String Methods in Python

Python provides a variety of built-in string methods to perform operations such as searching, replacing, splitting, etc.

Here are some commonly used string methods:

• len(): Returns the length of the string.
• upper(): Converts all characters in the string to uppercase.
• lower(): Converts all characters in the string to lowercase.
• replace(): Replaces a substring with another substring.
• strip(): Removes any leading or trailing whitespace.
• split(): Splits a string into a list based on a specified delimiter.
• join(): Joins elements of a list into a single string.

String Indexing and Slicing

In Python, you can access the characters of a string using indices.

text = "Python"
print(text[0])  # Output: P
print(text[-1])  # Output: n

Examples of Python String Methods

1. Finding Length of a String

text = "Python"
print(len(text))  # Output: 6

2. Converting to Uppercase

text = "hello world"
print(text.upper())  # Output: HELLO WORLD

3. Replacing Characters

text = "Hello World"
new_text = text.replace("World", "Python")
print(new_text)  # Output: Hello Python

4. Splitting Strings

text = "apple,banana,orange"
fruits = text.split(",")
print(fruits)  # Output: ['apple', 'banana', 'orange']

Real World Python String Tasks

Now lets see Python in action by solving sole real-world problems. By trying to solve real world problems through coding is the best way to understand and learn programming. The more task or problems you solve through coding, the better programmer you can become. Here are 20 real-world tasks that require string manipulation in Python. These tasks will help you understand how to apply string operations to solve everyday problems.

Task 1: Replacing Characters Without replace()

Write a program that replaces every occurrence of one character with another, without using the replace() method.

codetext = "Hello World"
result = ''
for char in text:
    if char == 'e':
        result += '6'
    elif char == 'l':
        result += '9'
    else:
        result += char
print(result)  # Output: H699o Wor9d

Task 2: Extract and Format Telephone Number

Given a string containing a 10-digit phone number, extract the area code, exchange, and number. Then format the output as a phone number.

codenumber = "1234567890"
area_code = number[:3]
exchange = number[3:6]
line_number = number[6:]
print(f"Area: {area_code}\nExchange: {exchange}\nNumber: {line_number}")
print(f"Formatted: ({area_code}){exchange}-{line_number}")

# Output:
# Area: 123
# Exchange: 456
# Number: 7890
# Formatted: (123)456-7890

Task 3: Extract Information from a String

Write a program to extract various details from a string like its length, first and last character, and position of a specific letter.

codetext = "To be or not to be!"
print(f"Length: {len(text)}")
print(f"First character: {text[0]}")
print(f"Last character: {text[-1]}")
print(f"Position of 'r': {text.find('r')}")

Task 4: Remove Spaces from a String

Convert a sentence to remove spaces between words.

codetext = "To be or not to be!"
result = text.replace(" ", "")
print(result)  # Output: ToBeOrNotToBe!

Task 5: Convert 2-Digit Year to 4-Digit Year

Convert a 2-digit year format into a 4-digit year format.

codedate = "06/30/98"
date = date[:6] + "19" + date[6:]
print(date)  # Output: 06/30/1998

Task 6: Format Name

Format a name into last-name-first format.

codename = "Abdul Jabbar Memon"
parts = name.split()
formatted_name = f"{parts[2]}, {parts[1]} {parts[0][0]}."
print(formatted_name)  # Output: Memon, Jabbar A.

Task 7: Convert Number to Words

Write a program that converts a 3-digit number to words.

codenum = 123
words = {
    100: "One Hundred",
    20: "Twenty",
    3: "Three"
}
print(f"{words[100]} {words[20]} {words[3]}")
# Output: One Hundred Twenty Three

Task 8: Date Conversion to Month Format

Convert a date string from “MM/DD/YY” format to “Month DD, YYYY” format.

codedate = "06/30/98"
month_names = {
    "06": "June"
}
new_date = f"{month_names[date[:2]]} – {date[3:5]} – 19{date[6:]}"
print(new_date)  # Output: June – 30 – 1998

Additional Real-World String Tasks

Now its your turn to solve the solve some these questions. solve them and leave the output in the comments below.

9. Find All Occurrences of a Substring in a String
10. Capitalize the First Letter of Each Word in a String
11. Check if a String is a Palindrome
12. Find the Most Frequent Character in a String
13. Check if a String Contains Only Digits
14. Count the Number of Words in a Sentence
15. Reverse a String Without Using Built-In Methods
16. Sort the Words in a String Alphabetically
17. Validate Email Format in a String
18. Remove Punctuation from a String
19. Check if Two Strings are Anagrams
20. Find the Longest Word in a Sentence

Conclusion:
String manipulation is an essential skill in Python programming. Whether you’re processing user input, generating reports, or cleaning up data, mastering Python’s string methods will give you the tools you need to tackle these tasks efficiently.

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Dr. Zeeshan Bhatti

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