Python Basics and Operators

In Python, you can assign values to variables with a simple equals sign. For example, a = expression evaluates the expression and stores the result in variable a.

The print() function displays values on the screen, while input() collects information from users. These are the building blocks of any interactive Python program.

Python includes several arithmetic operators that follow standard math order of operations. Besides the familiar +, -, *, /, and ** (exponentiation), Python has two special division operators:

• % (modulo): Returns the remainder after division (like 17 % 5 equals 2)
• // (integer division): Returns just the quotient without decimals (like 17 // 5 equals 3)

Pro tip: The modulo operator (%) is extremely useful for determining if a number is even or odd. If number % 2 == 0, the number is even!

Data Types

Python has several basic data types that store different kinds of information. The main ones you'll use include:

• int $like 1, 42, -5$: Whole numbers
• float (like 3.14, 0.001): Numbers with decimal points
• bool (True or False): Boolean values for logical operations
• str (like 'hello', "Python"): Text data

Booleans are particularly important for decision-making in your code. They're the result of comparison operations like <, >, ==, and !=. Remember that True and False must be capitalized in Python!

Strings represent text and can be created using either single quotes ('text') or double quotes ("text"). These are called string literals because you're literally writing out the text in your code.

Remember: Unlike other languages, Python is case-sensitive for everything, including Boolean values $`True`/`False`$, variable names, and function names.

Type Conversion (Casting)

Sometimes you need to convert data from one type to another - this is called casting. Python provides simple functions to handle this:

• int() converts values to integers (whole numbers)
• float() converts values to floating-point numbers
• str() converts values to strings

When casting decimal numbers to integers using int(), Python truncates the decimal portion rather than rounding. For example, int(1.8) becomes 1, not 2.

The input() function is crucial for interactive programs, allowing users to provide information to your program. It pauses your program until the user enters something and presses Enter.

Important: The input() function always returns data as a string, even if the user types numbers! If you need numeric values, you must cast the input using int() or float().

Working with User Input

Creating user-friendly programs means providing clear instructions about what input you expect. The input() function can display a prompt message by including it as an argument.

Instead of using separate lines like:

print('Enter a value:')
x = input()

You can combine them into a cleaner single statement:

x = input('Enter a value: ')

For calculations with user input, remember to convert string inputs to numbers first. You can do this in two ways:

1. Store the input, then convert: x = input('Value: ') followed by x = int(x)
2. Convert immediately: x = int(input('Value: '))

Both approaches work, but the second is more concise and often preferred by experienced programmers.

Quick tip: When asking for numeric input, include the type in your prompt message (like "Please enter an integer:") to help users provide the right format.

Helpful Python Notes

Python has some special characters and operators that come in handy when writing code. The newline character \n lets you add line breaks within strings, while # creates comments that help document your code but don't execute.

Remember to always cast user inputs when performing calculations. For example, int(input()) or float(input()) ensures you're working with numbers rather than text.

String concatenation uses the + operator to join strings together (like "Hello" + "World" becomes "HelloWorld"), while printing multiple items typically uses commas (like print("Value:", x)).

When performing division, the // operator gives you whole number results (integer division), while % gives you just the remainder. For example, 5 // 2 equals 2 and 5 % 2 equals 1.

Success tip: Keep this reference handy during practice exercises. You'll quickly memorize these operations as you use them regularly in your code!