3. Python Basics for Data Science

1. Variables and Data Types

name = "Alice" # String
age = 30 # Integer
height = 5.7 # Float
is_student = True # Boolean

In programming, variables are used to store data values. They act as containers that hold information which can be used and manipulated throughout the program. Python, the programming language we are using here, supports several basic data types.

• Strings: These are sequences of characters, enclosed in quotes. For example, name = 'Alice' stores the name 'Alice' as a string.
• Integers: Whole numbers that can be positive or negative, like age = 30.
• Floats: These are numbers that contain decimals, such as height = 5.7.
• Booleans: This data type has only two possible values: True or False, like is_student = True which indicates if someone is a student.

Think of variables like labeled containers in a workshop. Each container can hold a different kind of item: some containers are for liquids (like floats), some for solid items (like integers), some have labels showing names (like strings) and others might have a label showing if the item is present or not (like booleans). Just as you would use different containers to keep your workshop organized, programmers use different data types to manage information effectively.

2. Lists and Loops

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit.upper())

Lists in Python are ordered collections of items that can be of mixed types, such as strings, integers, and other lists. They are defined using square brackets. For instance, fruits = ["apple", "banana", "cherry"] creates a list of fruits.

Loops are used to iterate over items in a list. A common loop is the for loop, which allows you to execute a block of code repeatedly for each item in the collection. In this example, the loop goes through each item in the fruits list and prints it in uppercase, thanks to the method .upper().

Imagine you have a list of your favorite fruits written on a piece of paper. You want to tell someone these fruits, but you want to emphasize them by shouting their names. A list is like that piece of paper, and the loop is like you reading each fruit's name out loud in a loud voice. Each time you read a fruit's name, you make it all uppercase, implying enthusiasm, just like how the code transforms each fruit to uppercase letters.

3. Functions

def square(x):
    return x * x
print(square(5))

Functions in Python are reusable pieces of code that perform a specific task. They can be defined using the def keyword followed by the function name and parentheses. In the example, def square(x): defines a function called square that takes one parameter x. The function returns the value of x multiplied by itself (x * x), essentially calculating the square of a number. You can then call the function and pass a number to it, as shown by print(square(5)), which computes and displays the square of 5 (25).

Think of a function like a machine in a factory. You input something, like a number, and it processes it to produce an output. In our example, the square function is like a special machine that takes in a number and outputs its square, similar to how a cookie cutter takes a blob of dough and cuts it into a perfect cookie shape. You can use this machine as many times as you want with different input shapes (numbers).

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