Basic String Operations
Concatenate Strings
Exercise: Concatenate the strings “Hello” and “World” with a space in between.
Solution:
str1 = "Hello" str2 = "World" result = str1 + " " + str2
Explanation: Use the + operator to concatenate strings and include a space in between.
Repeat a String
Exercise: Repeat the string “Python” 3 times.
Solution:
result = "Python" * 3
Explanation: Use the * operator to repeat a string.
Access a Character by Index
Exercise: Get the 4th character from the string “Programming”.
Solution:
s = "Programming" char = s[3]
Explanation: String indexing starts at 0, so the 4th character is at index 3.
Slice a String
Exercise: Get the substring from index 2 to 5 of the string “DataScience”.
Solution:
s = "DataScience" substring = s[2:6]
Explanation: Use slicing to extract a portion of the string.
Find a Substring
Exercise: Find the index of the first occurrence of “code” in “Learn to code with code examples”.
Solution:
s = "Learn to code with code examples"
index = s.find("code")
Explanation: Use the find() method to locate the position of a substring.
Count Substring Occurrences
Exercise: Count how many times “is” appears in the string “This is a test. Is it correct?”.
Solution:
s = "This is a test. Is it correct?"
count = s.lower().count("is")
Explanation: Use count() to get the number of occurrences. Convert to lowercase to make it case-insensitive.
Check for Substring
Exercise: Check if the string “abc” is present in “abcdefg”.
Solution:
s = "abcdefg" contains = "abc" in s
Explanation: Use the in operator to check for substring presence.
Replace Substring
Exercise: Replace “good” with “bad” in the string “This is a good example.”.
Solution:
s = "This is a good example."
result = s.replace("good", "bad")
Explanation: Use replace() to substitute a substring with another.
Uppercase and Lowercase Conversion
Exercise: Convert the string “Hello World” to all uppercase and then all lowercase.
Solution:
s = "Hello World" uppercase = s.upper() lowercase = s.lower()
Explanation: Use upper() and lower() to change case.
Strip Whitespace
Exercise: Remove leading and trailing whitespace from ” Example “.
Solution:
s = " Example " stripped = s.strip()
Explanation: Use strip() to clean up whitespace.
String Formatting
Format Using f-strings
Exercise: Format the string “Hello {name}, you are {age} years old.” with name = “Alice” and age = 30.
Solution:
name = "Alice"
age = 30
result = f"Hello {name}, you are {age} years old."
Explanation: Use f-strings for easy string interpolation.
Old-Style Formatting
Exercise: Format the string “Temperature: %d°C” with 25 using old-style formatting.
Solution:
temp = 25 result = "Temperature: %d°C" % temp
Explanation: Use % for formatting.
Format with .format()
Exercise: Format the string “Your balance is ${:.2f}” with a balance of 1234.567.
Solution:
balance = 1234.567
result = "Your balance is ${:.2f}".format(balance)
Explanation: Use .format() for string formatting with precision.
Named Placeholders
Exercise: Format the string “Name: {name}, Age: {age}” with name = “Bob” and age = 45.
Solution:
result = "Name: {name}, Age: {age}".format(name="Bob", age=45)
Explanation: Use named placeholders in .format().
String Alignment
Exercise: Right-align the string “Hello” in a field of width 10.
Solution:
result = "{:>10}".format("Hello")
Explanation: Use {:>width} for right alignment.
Padding Strings
Exercise: Pad the string “data” with asterisks on both sides to make it 10 characters wide.
Solution:
result = "*{:^8}*".format("data")
Explanation: Use {:^width} for center alignment with padding.
String Methods
Check String Start
Exercise: Check if the string “Hello” starts with “He”.
Solution:
s = "Hello"
starts = s.startswith("He")
Explanation: Use startswith() to check the beginning of a string.
Check String End
Exercise: Check if the string “Python” ends with “on”.
Solution:
s = "Python"
ends = s.endswith("on")
Explanation: Use endswith() to check the end of a string.
Split a String
Exercise: Split the string “apple,banana,cherry” by commas.
Solution:
s = "apple,banana,cherry"
parts = s.split(",")
Explanation: Use split() to divide a string into a list.
Join Strings
Exercise: Join the list [“a”, “b”, “c”] into a single string with hyphens.
Solution:
parts = ["a", "b", "c"] result = "-".join(parts)
Explanation: Use join() to concatenate list elements into a string.
String Length
Exercise: Find the length of the string “Python Programming”.
Solution:
s = "Python Programming" length = len(s)
Explanation: Use len() to determine the number of characters.
String Case Checking
Exercise: Check if the string “Hello World” contains any uppercase letters.
Solution:
s = "Hello World" has_upper = any(c.isupper() for c in s)
Explanation: Use isupper() within a generator expression.
String Compression
Exercise: Convert the string “aaaabbbcccc” to a compressed format “4a3b4c”.
Solution:
from itertools import groupby
s = "aaaabbbcccc"
compressed = ''.join(f"{len(list(g))}{k}" for k, g in groupby(s))
Explanation: Use groupby() from itertools to compress repeated characters.
Remove Digits
Exercise: Remove all digits from the string “abc123def456”.
Solution:
import re s = "abc123def456" result = re.sub(r'\d+', '', s)
Explanation: Use regular expressions to remove digits.
Replace Multiple Substrings
Exercise: Replace “bad” with “good” and “wrong” with “right” in “This is bad and wrong.”.
Solution:
s = "This is bad and wrong."
result = s.replace("bad", "good").replace("wrong", "right")
Explanation: Chain replace() methods to handle multiple replacements.
Check for Alphanumeric
Exercise: Check if “abc123” is alphanumeric.
Solution:
s = "abc123" is_alphanumeric = s.isalnum()
Explanation: Use isalnum() to determine if all characters are alphanumeric.
Find All Occurrences
Exercise: Find all starting indices of the substring “is” in “This is a test. Is it correct?”.
Solution:
s = "This is a test. Is it correct?"
indices = [i for i in range(len(s)) if s.startswith("is", i)]
Explanation: Use a list comprehension with startswith() to find all occurrences.
Convert to Title Case
Exercise: Convert “hello world” to title case.
Solution:
s = "hello world" title_case = s.title()
Explanation: Use title() to capitalize the first letter of each word.
Convert to Swap Case
Exercise: Convert “Hello World” to swap case (upper becomes lower and vice versa).
Solution:
s = "Hello World" swapped_case = s.swapcase()
Explanation: Use swapcase() to swap the case of all characters.
Check if String is Numeric
Exercise: Check if the string “12345” is numeric.
Solution:
s = "12345" is_numeric = s.isdigit()
Explanation: Use isdigit() to check if the string consists of digits only.
Advanced String Manipulation
Extract Digits
Exercise: Extract all digits from the string “abc123def456”.
Solution:
import re s = "abc123def456" digits = re.findall(r'\d+', s)
Explanation: Use re.findall() to extract all digit sequences.
Remove Punctuation
Exercise: Remove all punctuation from “Hello, world!”.
Solution:
import string
s = "Hello, world!"
result = s.translate(str.maketrans('', '', string.punctuation))
Explanation: Use str.translate() with str.maketrans() to remove punctuation.
Check Palindrome
Exercise: Check if “A man a plan a canal Panama” is a palindrome (ignore spaces and case).
Solution:
s = "A man a plan a canal Panama" cleaned = ''.join(c.lower() for c in s if c.isalnum()) is_palindrome = cleaned == cleaned[::-1]
Explanation: Clean the string and check if it reads the same forwards and backwards.
Replace with Regular Expression
Exercise: Replace all sequences of digits in “Price: $1000, $2000” with “XXX”.
Solution:
import re s = "Price: $1000, $2000" result = re.sub(r'\d+', 'XXX', s)
Explanation: Use re.sub() to replace patterns matched by a regular expression.
Extract Email Username
Exercise: Extract the username from the email “user@example.com”.
Solution:
email = "user@example.com"
username = email.split('@')[0]
Explanation: Split the string at ‘@’ and take the first part.
Reverse a String
Exercise: Reverse the string “Hello” to “olleH”.
Solution:
s = "Hello" reversed_s = s[::-1]
Explanation: Use slicing with [::-1] to reverse the string.
Check String Equality Ignoring Case
Exercise: Check if “hello” is equal to “HELLO” ignoring case.
Solution:
s1 = "hello" s2 = "HELLO" equal = s1.lower() == s2.lower()
Explanation: Convert both strings to lowercase before comparison.
Find the Longest Word
Exercise: Find the longest word in the string “I love programming in Python”.
Solution:
s = "I love programming in Python" longest_word = max(s.split(), key=len)
Explanation: Split the string into words and use max() with key=len to find the longest.
Extract File Extension
Exercise: Extract the file extension from the filename “report.pdf”.
Solution:
filename = "report.pdf"
extension = filename.split('.')[-1]
Explanation: Split the filename by ‘.’ and get the last part.
Remove Specific Characters
Exercise: Remove all occurrences of “a” and “b” from “abracadabra”.
Solution:
s = "abracadabra"
result = s.translate(str.maketrans('', '', 'ab'))
Explanation: Use str.translate() with str.maketrans() to remove specific characters.