Python Classroom notes 01/Sep/2024

Lets solve some problems

Exercise 1: FizzBuzz Variation

• Problem: Write a function called fizzbuzz_variant(n) that takes an integer n and returns a list of numbers from 1 to n. For multiples of three, append "Fizz" instead of the number, for multiples of five append "Buzz", and for multiples of both three and five append "FizzBuzz".
• Expected Output:
  python
fizzbuzz_variant(15)
# Output: [1, 2, "Fizz", 4, "Buzz", "Fizz", 7, 8, "Fizz", "Buzz", 11, "Fizz", 13, 14, "FizzBuzz"]

Exercise 2: Factorial with Recursion

• Problem: Write a recursive function factorial(n) that returns the factorial of a given number n.
• Expected Output:
  python
factorial(5)
# Output: 120

Exercise 3: List Comprehension Practice

• Problem: Create a function squares_of_even_numbers(nums) that takes a list of integers and returns a list of the squares of all even numbers in the list using list comprehension.
• Expected Output:
  python
squares_of_even_numbers([1, 2, 3, 4, 5, 6])
# Output: [4, 16, 36]

Exercise 4: Palindrome Checker

• Problem: Write a function is_palindrome(s) that takes a string s and returns True if it is a palindrome (reads the same forwards and backwards), and False otherwise.
• Expected Output:
  python
is_palindrome("racecar")
# Output: True

Exercise 5: Dictionary Manipulation

• Problem: Write a function invert_dict(d) that takes a dictionary d and returns a new dictionary where the keys are the values and the values are the keys.
• Expected Output:
  python
invert_dict({"a": 1, "b": 2, "c": 3})
# Output: {1: "a", 2: "b", 3: "c"}

Exercise 6: String Manipulation

• Problem: Write a function vowel_count(s) that takes a string s and returns a dictionary with vowels as keys and their counts as values.
• Expected Output:
  python
vowel_count("hello world")
# Output: {"e": 1, "o": 2}

Exercise 7: Nested Loops: Multiplication Table

• Problem: Write a function multiplication_table(n) that prints the multiplication table of size n.
• Expected Output:
  python
multiplication_table(3)
# Output:
# 1 2 3
# 2 4 6
# 3 6 9

Exercise 8: Prime Number Checker

• Problem: Write a function is_prime(n) that returns True if n is a prime number and False otherwise.
• Expected Output:
  python
is_prime(11)
# Output: True

Exercise 9: Sum of Digits

• Problem: Write a function sum_of_digits(n) that takes a positive integer n and returns the sum of its digits.
• Expected Output:
  python
sum_of_digits(1234)
# Output: 10

Exercise 10: Custom Sorting

• Problem: Write a function custom_sort(strings) that takes a list of strings and returns it sorted by the length of each string.
• Expected Output:
  python
custom_sort(["apple", "pie", "banana", "kiwi"])
# Output: ["pie", "kiwi", "apple", "banana"]

Exercise 11: GCD (Greatest Common Divisor)

• Problem: Write a function gcd(a, b) that returns the greatest common divisor of two integers a and b.
• Expected Output:
  python
gcd(48, 18)
# Output: 6

Exercise 12: Caesar Cipher

• Problem: Implement a function caesar_cipher(text, shift) that takes a string text and an integer shift, and returns the encoded text by shifting each letter by the given number in the alphabet. Assume the text contains only lowercase letters.
• Expected Output:
  python
caesar_cipher("abc", 3)
# Output: "def"

Exercise 13: Flatten a Nested List

• Problem: Write a function flatten_list(nested_list) that takes a nested list of integers and returns a flattened list.
• Expected Output:
  python
flatten_list([[1, 2, [3]], [4, 5], [6, [7, 8]]])
# Output: [1, 2, 3, 4, 5, 6, 7, 8]

Exercise 14: Fibonacci Sequence

• Problem: Write a function fibonacci(n) that returns the first n numbers in the Fibonacci sequence.
• Expected Output:
  python
fibonacci(7)
# Output: [0, 1, 1, 2, 3, 5, 8]

Exercise 15: Anagram Checker

• Problem: Write a function are_anagrams(s1, s2) that takes two strings s1 and s2 and returns True if they are anagrams of each other, and False otherwise.
• Expected Output:
  python
are_anagrams("listen", "silent")
# Output: True

Exercise 16: Unique Elements

• Problem: Write a function unique_elements(lst) that takes a list of integers and returns a list with only the unique elements, preserving the original order.
• Expected Output:
  python
unique_elements([1, 2, 2, 3, 4, 4, 5])
# Output: [1, 2, 3, 4, 5]

Exercise 17: Transpose a Matrix

• Problem: Write a function transpose_matrix(matrix) that takes a 2D list (matrix) and returns its transpose.
• Expected Output:
  python
transpose_matrix([[1, 2], [3, 4], [5, 6]])
# Output: [[1, 3, 5], [2, 4, 6]]

Exercise 18: Sum of Squares

• Problem: Write a function sum_of_squares(n) that returns the sum of the squares of all positive integers up to and including n.
• Expected Output:
  python
sum_of_squares(5)
# Output: 55 (1^2 + 2^2 + 3^2 + 4^2 + 5^2)

Exercise 19: Letter Frequency

• Problem: Write a function letter_frequency(s) that takes a string s and returns a dictionary with the frequency of each letter in the string.
• Expected Output:
  python
letter_frequency("hello")
# Output: {"h": 1, "e": 1, "l": 2, "o": 1}

Exercise 20: Generate a List of Primes

• Problem: Write a function generate_primes(n) that returns a list of prime numbers up to n.
• Expected Output:
  python
generate_primes(10)
# Output: [2, 3, 5, 7]

Exercise 21: Merge Two Sorted Lists

• Problem: Write a function merge_sorted_lists(list1, list2) that merges two sorted lists into a single sorted list.
• Expected Output:
  python
merge_sorted_lists([1, 3, 5], [2, 4, 6])
# Output: [1, 2, 3, 4, 5, 6]

Exercise 22: Longest Word in a Sentence

• Problem: Write a function longest_word(sentence) that takes a string sentence and returns the longest word in the sentence.
• Expected Output:
  python
longest_word("The quick brown fox jumps over the lazy dog")
# Output: "jumps"

Exercise 23: Remove Duplicates from a List

• Problem: Write a function remove_duplicates(lst) that takes a list and returns a new list with all duplicate elements removed.
• Expected Output:
  python
remove_duplicates([1, 2, 2, 3, 4, 4, 5])
# Output: [1, 2, 3, 4, 5]

Exercise 24: Check for a Pangram

• Problem: Write a function is_pangram(s) that checks whether a given string s is a pangram (contains every letter of the alphabet at least once).
• Expected Output:
  python
is_pangram("The quick brown fox jumps over the lazy dog")
# Output: True

Exercise 25: Find the Second Largest Element

• Problem: Write a function second_largest(lst) that returns the second largest element in a list of integers.
• Expected Output:
  python
second_largest([10, 20, 4, 45, 99])
# Output: 45

Lambda

• Lambda functions Refer Here
• Lambda function is a function without name

lambda : expression

lambda arg: expression

List Comprehensions

• Refer Here for samples

Dictionary Comprehensions

• Refer Here for dictionary comprehensions

Python Standard Library

1. Introduction to Python Standard Library

• What is the Python Standard Library?
  • A collection of modules and packages included with Python.
  • Provides tools for various tasks like file handling, networking, math, and more.

2. Commonly Used Modules

2.1 os Module

• Working with the Operating System:
  • os.getcwd() – Get current working directory.
  • os.listdir() – List files in a directory.
  • os.mkdir() – Create a directory.
  • os.remove() – Delete a file.

2.2 sys Module

• System-Specific Parameters and Functions:
  • sys.argv – Command line arguments.
  • sys.exit() – Exit from Python.
  • sys.path – List of directories Python looks for modules.

2.3 math Module

• Mathematical Functions:
  • math.sqrt() – Square root.
  • math.factorial() – Factorial of a number.
  • math.pi – Value of Ï€.
  • math.sin(), math.cos(), math.tan() – Trigonometric functions.

2.4 datetime Module

• Date and Time Handling:
  • datetime.date() – Date object.
  • datetime.time() – Time object.
  • datetime.datetime.now() – Current date and time.
  • datetime.timedelta() – Time differences.

2.5 random Module

• Random Number Generation:
  • random.randint() – Random integer.
  • random.choice() – Randomly choose from a list.
  • random.shuffle() – Shuffle a list.
  • random.sample() – Random sample from a list.

2.6 re Module

• Regular Expressions:
  • re.match() – Match a pattern.
  • re.search() – Search for a pattern.
  • re.findall() – Find all occurrences.
  • re.sub() – Substitute strings.

2.7 json Module

• JSON Handling:
  • json.dumps() – Convert Python object to JSON string.
  • json.loads() – Parse JSON string into Python object.
  • json.dump() – Write JSON data to a file.
  • json.load() – Load JSON data from a file.

2.8 collections Module

• Advanced Data Structures:
  • Counter – Count elements in an iterable.
  • deque – Double-ended queue.
  • defaultdict – Dictionary with a default value.
  • namedtuple – Tuple with named fields.

3. File Handling with io and os

• Reading and Writing Files:
  • open(), read(), write(), close() methods.
  • File modes (r, w, a, b).
• Context Managers:
  • Using with statement for file handling.

4. Networking with socket and http

• Creating a Basic Server and Client:
  • socket.socket() – Create a socket.
  • socket.bind(), socket.listen(), socket.accept() – Server functions.
  • socket.connect(), socket.send(), socket.recv() – Client functions.
• HTTP Requests with http.client and urllib Modules:
  • urllib.request.urlopen() – Open a URL.
  • http.client.HTTPConnection() – Manage HTTP connections.

5. Error Handling with exceptions

• Common Exceptions:
  • try, except, finally blocks.
  • raise – Trigger an exception.
  • Custom exceptions by subclassing Exception.

6. Concurrency with threading and multiprocessing

• Creating Threads and Processes:
  • threading.Thread() – Create a new thread.
  • multiprocessing.Process() – Create a new process.
• Synchronizing Threads:
  • threading.Lock(), threading.Semaphore().

7. Unit Testing with unittest

• Writing Test Cases:
  • unittest.TestCase – Base class for writing tests.
  • assertEqual(), assertTrue(), assertRaises() – Common assertions.
• Running Tests:
  • unittest.main() – Run all tests.

8. Data Compression and Archiving with zipfile, tarfile, and gzip

• Creating and Extracting Archives:
  • zipfile.ZipFile() – Work with zip files.
  • tarfile.open() – Work with tar files.
  • gzip.open() – Work with gzip files.

9. Conclusion and Further Learning

• Exploring Lesser-Known Modules:
  • itertools, functools, enum, pdb (debugger).
• Official Python Documentation:
  • Python Standard Library Documentation

Lets recreate vowel count with defaultdict, comprehnension and Counter

• count characters in a string

Lets understand modules and packages

• Look into classroom recording