Variables and Data Types

Variables are how you store and work with data in Python. Unlike many languages, Python doesn't require you to declare a variable's type — it figures it out automatically.

Creating Variables

Just use = to assign a value to a name:

message = "Hello"
count = 42
temperature = 98.6
is_active = True

message = "Hello"
count = 42
temperature = 98.6
is_active = True

print(message)
print(count)
print(temperature)
print(is_active)

Click "Run" to execute your code

Naming Rules

Variable names in Python:

• Must start with a letter or underscore (_)
• Can contain letters, numbers, and underscores
• Are case-sensitive (name and Name are different)
• Cannot be Python keywords (if, for, class, etc.)

By convention, Python uses snake_case for variable names:

first_name = "Alice"     # Good
firstName = "Alice"      # Works, but not Pythonic

Data Types

Python has several built-in data types:

Type	Example	Description
int	42	Whole numbers
float	3.14	Decimal numbers
str	"hello"	Text strings
bool	True / False	Boolean values
None	None	Absence of a value

Use type() to check a variable's type:

print(type(42))        # <class 'int'>
print(type(3.14))      # <class 'float'>
print(type("hello"))   # <class 'str'>
print(type(True))      # <class 'bool'>

x = 42
y = 3.14
z = "hello"
w = True

print(f"{x} is {type(x)}")
print(f"{y} is {type(y)}")
print(f"{z} is {type(z)}")
print(f"{w} is {type(w)}")

Click "Run" to execute your code

Strings

Strings are sequences of characters. You can use single or double quotes:

single = 'Hello'
double = "Hello"
multi = """This is a
multi-line string"""

F-Strings (Formatted Strings)

F-strings let you embed expressions inside strings:

name = "Alice"
age = 30
print(f"My name is {name} and I am {age} years old.")
print(f"Next year I'll be {age + 1}.")

Type Conversion

Convert between types using built-in functions:

# String to number
x = int("42")       # 42
y = float("3.14")   # 3.14

# Number to string
s = str(42)          # "42"

# Check truthiness
bool(0)              # False
bool(1)              # True
bool("")             # False
bool("hello")        # True

# Type conversion
age_str = "25"
age_num = int(age_str)

print(f"In 5 years: {age_num + 5}")
print(f"Type: {type(age_num)}")

# Truthiness
print(f"bool(0) = {bool(0)}")
print(f'bool("") = {bool("")}')
print(f"bool(42) = {bool(42)}")
print(f'bool("hi") = {bool("hi")}')

Click "Run" to execute your code

Multiple Assignment

Python lets you assign multiple variables at once:

x, y, z = 1, 2, 3
a = b = c = 0

What's Next?

Now that you understand variables and types, you're ready to explore Python's powerful built-in data structures. Check out the Reference section for detailed docs on strings and lists.