Phase 01: Foundations of Python and Mathematics

Day 01: Python Basics Refresher

📑 Table of Contents

🌟 Welcome to Day 1
🐍 Python Basics
- Variables and Data Types
- Operators
- Control Structures
- Functions
- Modules and Packages
💻 Hands-On Coding
- Example Script: Interactive Calculator
🧩 Interactive Exercises
📚 Resources
💡 Tips and Tricks

1. 🌟 Welcome to Day 1

Welcome to Day 1 of "Becoming a Scikit-Learn Boss in 90 Days"! 🎉 Today, we kickstart our journey by refreshering Python basics. Whether you're a seasoned programmer or just starting, revisiting these fundamentals will ensure you're well-prepared for the advanced topics ahead. Let's dive in and set a strong foundation for your machine learning endeavors! 🚀

2. 🐍 Python Basics

📝 Variables and Data Types

Variables are the building blocks of any programming language. They store data that can be manipulated and used throughout your code. Python offers various data types to handle different kinds of data.

Integers (int): Whole numbers without a decimal point.
```
age = 25
year = 2024
```
Floating-point (float): Numbers with decimal points.
```
pi = 3.1416
temperature = 36.6
```
Strings (str): Sequences of characters enclosed in quotes.
```
name = "Alice"
greeting = 'Hello, World!'
```
Booleans (bool): Represent logical values, either True or False.
```
is_student = True
has_graduated = False
```

🧩 Try It Yourself!

Create variables of different data types and print their values.

# Define variables
age = 30
height = 5.9
name = "Bob"
is_employed = True

# Print variables
print(age, height, name, is_employed)

⚙️ Operators

Operators allow you to perform operations on variables and values. Python supports several types of operators:

Arithmetic Operators: +, -, *, /, %, **, //

a = 10
b = 3
print(a + b)  # 13
print(a ** b) # 1000

Comparison Operators: ==, !=, >, <, >=, <=

print(a > b)  # True
print(a == b) # False

Logical Operators: and, or, not

print(a > 5 and b < 5)  # True
print(not(a > 15))      # True

🧩 Try It Yourself!

Write a script that takes two numbers as input and performs all arithmetic operations.

# Input numbers
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))

# Perform operations
addition = num1 + num2
subtraction = num1 - num2
multiplication = num1 * num2
division = num1 / num2 if num2 != 0 else "Undefined"

# Display results
print(f"Addition: {addition}")
print(f"Subtraction: {subtraction}")
print(f"Multiplication: {multiplication}")
print(f"Division: {division}")

# Bonus: Comparison
if num1 > num2:
    print(f"{num1} is greater than {num2}.")
elif num1 < num2:
    print(f"{num1} is less than {num2}.")
else:
    print(f"Both numbers are equal.")

🔄 Control Structures

Control structures dictate the flow of your program. The primary ones in Python are conditional statements and loops.

🔺 Conditional Statements

if Statement: Executes a block of code if a condition is true.
elif Statement: Checks another condition if the previous if was false.
else Statement: Executes a block of code if all previous conditions are false.

Example:

age = 20

if age >= 18:
    print("You are an adult.")
elif age > 13:
    print("You are a teenager.")
else:
    print("You are a child.")

🔁 Loops

for Loop: Iterates over a sequence (like a list, tuple, or string).
while Loop: Repeats as long as a condition is true.

Example:

# For Loop
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

# While Loop
count = 0
while count < 5:
    print(count)
    count += 1

🧩 Try It Yourself!

Create a program that checks if a number is positive, negative, or zero.

# Check if a number is positive, negative, or zero
num = float(input("Enter a number: "))

if num > 0:
    print("Positive number")
elif num == 0:
    print("Zero")
else:
    print("Negative number")

# Bonus: Print all even numbers from 1 to 20
print("Even numbers from 1 to 20:")
for i in range(1, 21):
    if i % 2 == 0:
        print(i, end=' ')

🔧 Functions

Functions are reusable blocks of code that perform specific tasks. They help in organizing code and avoiding repetition.

Defining a Function:

def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))

Functions with Default Parameters:

def power(base, exponent=2):
    return base ** exponent

print(power(3))       # Uses default exponent 2
print(power(3, 3))    # Uses exponent 3

Example:
Create a function that calculates the factorial of a number.

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

print(factorial(5))  # Output: 120

🧩 Try It Yourself!

Define a function that takes a list of numbers and returns the largest number.

def find_max(numbers):
    if not numbers:
        return None
    max_num = numbers[0]
    for num in numbers:
        if num > max_num:
            max_num = num
    return max_num

print(find_max([3, 1, 4, 1, 5, 9, 2]))  # Output: 9

# Bonus: Function to check if a string is a palindrome
def is_palindrome(s):
    s = s.lower().replace(" ", "")
    return s == s[::-1]

print(is_palindrome("Racecar"))  # Output: True
print(is_palindrome("Hello"))    # Output: False

📦 Modules and Packages

Modules are Python files containing functions, classes, or variables that you can include in your project. Packages are collections of modules organized in directories.

📥 Importing a Module

import math

print(math.sqrt(16))  # Output: 4.0

📥 Importing Specific Functions

from math import pi, sin

print(pi)          # Output: 3.141592653589793
print(sin(pi / 2)) # Output: 1.0

🛠️ Creating Your Own Module

Create a Python file (e.g., math_utils.py):

# math_utils.py
def multiply(a, b):
    return a * b

def divide(a, b):
    if b == 0:
        return "Cannot divide by zero!"
    return a / b

Import and Use the Module:

import math_utils

print(math_utils.multiply(4, 5))  # Output: 20
print(math_utils.divide(10, 2))   # Output: 5.0
print(math_utils.divide(10, 0))   # Output: Cannot divide by zero!

🧩 Try It Yourself!

Create your own module with at least two functions and import them into another script.

# Create a file named 'string_utils.py'

def to_uppercase(s):
    return s.upper()

def to_lowercase(s):
    return s.lower()

# Another script to import and use 'string_utils.py'

import string_utils

print(string_utils.to_uppercase("hello"))  # Output: HELLO
print(string_utils.to_lowercase("WORLD"))  # Output: world

3. 💻 Hands-On Coding

🎉 Example Script: Interactive Calculator 🎉

Let's build a simple interactive calculator that can perform basic arithmetic operations. This script will allow users to choose an operation and input numbers to get results in real-time.

Script: Day1_Python_Basics_Refresher.py

def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

def multiply(a, b):
    return a * b

def divide(a, b):
    if b == 0:
        return "Error! Division by zero."
    return a / b

def main():
    while True:
        print("\n--- Simple Calculator ---")
        print("Select operation:")
        print("1. Add")
        print("2. Subtract")
        print("3. Multiply")
        print("4. Divide")
        print("5. Exit")

        choice = input("Enter choice (1/2/3/4/5): ")

        if choice == '5':
            print("Thank you for using the calculator. Goodbye!")
            break

        if choice in ['1', '2', '3', '4']:
            try:
                num1 = float(input("Enter first number: "))
                num2 = float(input("Enter second number: "))
            except ValueError:
                print("Invalid input! Please enter numeric values.")
                continue

            if choice == '1':
                print(f"{num1} + {num2} = {add(num1, num2)}")
            elif choice == '2':
                print(f"{num1} - {num2} = {subtract(num1, num2)}")
            elif choice == '3':
                print(f"{num1} * {num2} = {multiply(num1, num2)}")
            elif choice == '4':
                result = divide(num1, num2)
                print(f"{num1} / {num2} = {result}")
        else:
            print("Invalid input! Please choose a valid operation.")

if __name__ == "__main__":
    main()

🚀 How to Run:

Navigate to the Scripts directory:

cd Phase1_Foundations_of_Python_and_Mathematics/Day1_Python_Basics_Refresher/Scripts

Execute the script:
```
python Day1_Python_Basics_Refresher.py
```
Follow the on-screen instructions to perform calculations.

🖥️ Sample Interaction:

--- Simple Calculator ---
Select operation:
1. Add
2. Subtract
3. Multiply
4. Divide
5. Exit
Enter choice (1/2/3/4/5): 1
Enter first number: 10
Enter second number: 5
10.0 + 5.0 = 15.0

--- Simple Calculator ---
Select operation:
1. Add
2. Subtract
3. Multiply
4. Divide
5. Exit
Enter choice (1/2/3/4/5): 4
Enter first number: 10
Enter second number: 0
10.0 / 0.0 = Error! Division by zero.

--- Simple Calculator ---
Select operation:
1. Add
2. Subtract
3. Multiply
4. Divide
5. Exit
Enter choice (1/2/3/4/5): 5
Thank you for using the calculator. Goodbye!

4. 🧩 Interactive Exercises

📝 Exercise 1: Variables and Data Types

Task: Declare variables of different data types and print their values.
Bonus: Convert a string to an integer and perform arithmetic operations.

# Define variables
temperature = 23.5    # float
city = "New York"     # string
is_raining = False    # boolean

# Print variables
print(temperature, city, is_raining)

# Bonus: Convert string to integer
str_num = "100"
int_num = int(str_num)
print(int_num + 50)    # Output: 150

📝 Exercise 2: Operators

Task: Write a script that takes two numbers as input and performs all arithmetic operations.
Bonus: Compare two numbers and print which one is greater or if they are equal.

# Input numbers
num1 = float(input("Enter first number: "))
num2 = float(input("Enter second number: "))

# Perform operations
addition = num1 + num2
subtraction = num1 - num2
multiplication = num1 * num2
division = num1 / num2 if num2 != 0 else "Undefined"

# Display results
print(f"Addition: {addition}")
print(f"Subtraction: {subtraction}")
print(f"Multiplication: {multiplication}")
print(f"Division: {division}")

# Bonus: Comparison
if num1 > num2:
    print(f"{num1} is greater than {num2}.")
elif num1 < num2:
    print(f"{num1} is less than {num2}.")
else:
    print(f"Both numbers are equal.")

📝 Exercise 3: Control Structures

Task: Create a program that checks if a number is positive, negative, or zero.
Bonus: Write a loop that prints all even numbers from 1 to 20.

# Check if a number is positive, negative, or zero
num = float(input("Enter a number: "))

if num > 0:
    print("Positive number")
elif num == 0:
    print("Zero")
else:
    print("Negative number")

# Bonus: Print all even numbers from 1 to 20
print("Even numbers from 1 to 20:")
for i in range(1, 21):
    if i % 2 == 0:
        print(i, end=' ')

📝 Exercise 4: Functions

Task: Define a function that takes a list of numbers and returns the largest number.
Bonus: Create a function that checks if a string is a palindrome.

# Function to find the largest number in a list
def find_max(numbers):
    if not numbers:
        return None
    max_num = numbers[0]
    for num in numbers:
        if num > max_num:
            max_num = num
    return max_num

print(find_max([3, 1, 4, 1, 5, 9, 2]))  # Output: 9

# Bonus: Function to check if a string is a palindrome
def is_palindrome(s):
    s = s.lower().replace(" ", "")
    return s == s[::-1]

print(is_palindrome("Racecar"))  # Output: True
print(is_palindrome("Hello"))    # Output: False

📝 Exercise 5: Modules and Packages

Task: Use the random module to generate a random number between 1 and 100.
Bonus: Create your own module with at least two functions and import them into another script.

import random

# Generate a random number between 1 and 100
random_num = random.randint(1, 100)
print(f"Random Number: {random_num}")

# Bonus: Using your own module
import math_utils

print(math_utils.multiply(4, 5))  # Output: 20
print(math_utils.divide(10, 2))   # Output: 5.0
print(math_utils.divide(10, 0))   # Output: Cannot divide by zero!

5. 📚 Resources

Enhance your learning with these excellent resources:

6. 💡 Tips and Tricks

💡 Pro Tip

Virtual Environments: Always use virtual environments to manage your project dependencies. This keeps your projects isolated and prevents version conflicts.

# Create a virtual environment
python3 -m venv my_env

# Activate the virtual environment
source my_env/bin/activate  # On Windows: my_env\Scripts\activate

# Install packages
pip install package_name

🛠️ Recommended Tools

Visual Studio Code: A powerful code editor with Python extensions.
PyCharm: An IDE specifically designed for Python development.
Jupyter Notebook: Interactive notebooks for data analysis and visualization.

🚀 Speed Up Your Coding

Use List Comprehensions: They provide a concise way to create lists.
```
squares = [x**2 for x in range(10)]
```

Leverage Built-in Functions: Python's standard library offers a plethora of useful functions.

numbers = [1, 2, 3, 4, 5]
print(sum(numbers))  # Output: 15
print(max(numbers))  # Output: 5

🔍 Debugging Tips

Use Print Statements: Simple yet effective for tracking variable values.
Leverage Debuggers: Tools like the built-in debugger in VS Code can help step through your code.

Handle Exceptions: Gracefully handle errors to prevent your program from crashing.

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero!")

Thank You Animation

Code Files: Day1 Python Basics Refresher

Phase 01: Foundations of Python and Mathematics