Variables, Data Types & Operators

What you'll learn

Every program is really just data being stored, changed, and combined. In this module you'll learn how Python holds data in variables, the types that data can take, and the operators you use to calculate and compare — including a few Python surprises.

By the end you'll be able to:

• Create variables and understand Python's dynamic typing
• Work with the core types: int, float, str, bool, and None
• Convert between types safely with int(), float(), and str()
• Use arithmetic operators — including Python's special /, //, and **
• Apply comparison, logical, and bitwise operators
• Predict results using operator precedence

Variables & dynamic typing

A variable is a name that refers to a value. Creating one couldn't be simpler — you just assign with =. There's no type declaration and no special keyword; Python figures out the type from the value:

age = 25            # an int
price = 19.99       # a float
name = "Sara"       # a str
is_student = True   # a bool

print(age)
print(name, "-", price)

Python is dynamically typed: a variable is really just a label attached to an object, and you can re-attach that label to a value of a different type at any time. Use the built-in type() function to ask what type a value currently is:

x = 5
print(type(x))          # <class 'int'>

x = "now I'm a string"  # totally fine — x can change type
print(type(x))          # <class 'str'>

x = [1, 2, 3]
print(type(x))          # <class 'list'>

The core data types

You'll meet many types, but a handful cover almost everything you do early on:

whole = 42
pi = 3.14159
big = 1_000_000        # underscores just aid readability
c = 2 + 3j             # a complex number

print(type(whole), type(pi))
print(big)
print(2 ** 100)        # Python ints never overflow!

Type conversion

Because Python won't mix types automatically, you convert values yourself using the type's name as a function: int(), float(), str(), bool(). This matters constantly — input() (Module 4) always gives you a str, so you must convert it before doing maths:

# input() always returns a str — convert it to do maths
age_text = "25"
age = int(age_text)
print(age + 5)          # 30

print(float("19.99"))   # 19.99
print("Count: " + str(42))   # str() to join with text
print(int(3.9))         # 3  (truncates — does NOT round)
print(bool(0), bool(1)) # False True

Arithmetic operators

The maths operators look familiar, but Python has three worth special attention — and the first one trips up newcomers from other languages:

a, b = 17, 5

print(a + b)     # 22
print(a - b)     # 12
print(a * b)     # 85
print(a / b)     # 3.4    <- true division ALWAYS gives a float
print(a // b)    # 3      <- floor (integer) division
print(a % b)     # 2      <- remainder (modulo)
print(a ** b)    # 1419857 <- 17 to the power of 5

Comparison & logical operators

Comparison operators ask a yes/no question and produce a bool, while logical operators combine those booleans. Python has a lovely feature here — you can chain comparisons the way you would in maths:

age = 20

print(age >= 18)             # True
print(13 <= age <= 19)       # False  (chained comparison!)
print(age > 0 and age < 100) # True
print(not age == 21)         # True

Bitwise operators

For working with the individual bits of integers — useful for flags, low-level code, and some algorithms — Python offers bitwise operators:

print(5 & 3)    # 1   bitwise AND
print(5 | 3)    # 7   bitwise OR
print(5 ^ 3)    # 6   bitwise XOR
print(1 << 4)   # 16  left shift (1 * 2**4)

Operator precedence

When several operators appear together, precedence decides who goes first — just like maths, where * beats +. From highest to lowest, simplified:

Recap & quick check

Great work — you can now store and manipulate data with confidence. Next up: Module 3 — Strings & Formatting, where you'll master Python's powerful text type.