Python Variables and Data Types: A Complete Guide

April 19, 2026 Python Basics 8 min read

Variables are the foundation of every Python program. Before you can write a loop, define a function, or build an algorithm, you need a place to store data β€” and that's exactly what a variable gives you. In this guide you'll learn how to create variables, which data types Python provides, and how to convert between them.

What Is a Variable?

A variable is a named label that points to a value stored in memory. You create one with a simple assignment statement using the = operator:

python 
# Assign a value to a variable
crop_name = "wheat"
plot_count = 12
growth_rate = 1.5
is_irrigated = True

print(crop_name)    # wheat
print(plot_count)   # 12

Naming rules to keep in mind:

  • Use lowercase letters and underscores: crop_name, not CropName or cropname.
  • Names must start with a letter or underscore β€” never a digit.
  • No spaces allowed; use underscores instead.
  • Avoid Python's reserved keywords (if, for, return, etc.).
Tip: Descriptive names like harvest_yield beat cryptic ones like hy. Your future self will thank you.

Basic Data Types

Python has several built-in types. You don't need to declare them β€” Python infers the type from the value you assign.

int β€” integers

Whole numbers, positive or negative, with no decimal point.

python 
gold = 250
plots_owned = 6
seeds_in_bag = -3   # negative ints are valid

print(type(gold))   # <class 'int'>

float β€” decimal numbers

Numbers with a fractional part. Python uses 64-bit double precision floats.

python 
growth_rate = 1.5
water_level = 0.75
temperature = -2.3

print(type(growth_rate))  # <class 'float'>

str β€” strings

Text data, enclosed in single or double quotes. Strings are immutable β€” once created, the characters cannot be changed in place.

python 
crop_name = "wheat"
message = 'Harvest ready!'
multiline = """Season 3
Day 12"""

# String concatenation
greeting = "Hello, " + crop_name + "!"
print(greeting)   # Hello, wheat!

# f-strings (the modern way)
info = f"{crop_name} grows at rate {growth_rate}"
print(info)       # wheat grows at rate 1.5

bool β€” booleans

Only two possible values: True or False. Note the capital first letter β€” Python is case-sensitive.

python 
is_mature = True
is_watered = False

print(type(is_mature))   # <class 'bool'>
print(is_mature and is_watered)   # False
print(is_mature or is_watered)    # True

None β€” the absence of a value

None represents "nothing" or "no value yet." It's Python's equivalent of null in other languages.

python 
selected_crop = None   # player hasn't chosen yet

if selected_crop is None:
    print("Please select a crop first.")
else:
    print(f"Planting {selected_crop}.")

Dynamic Typing

Python is dynamically typed, meaning a variable can be reassigned to a value of a completely different type. The variable doesn't have a fixed type β€” the value does.

python 
score = 100           # int
print(type(score))    # <class 'int'>

score = "high"        # now it's a str
print(type(score))    # <class 'str'>

# Check type with isinstance()
value = 3.14
print(isinstance(value, float))   # True
print(isinstance(value, int))     # False
Note: Dynamic typing is powerful but requires care. If you expect a number and get a string, arithmetic will raise a TypeError. Use isinstance() to guard against this.

Type Conversion

You can explicitly convert between types using built-in functions: int(), float(), str(), and bool().

python 
user_input = "42"          # from input() β€” always a string
gold_earned = int(user_input) + 10
print(gold_earned)         # 52

price = 9.99
print(int(price))          # 9  (truncates, does NOT round)
print(str(price))          # "9.99"
print(float("3.5"))        # 3.5

# bool() β€” falsy values become False
print(bool(0))             # False
print(bool(""))            # False
print(bool(42))            # True
print(bool("wheat"))       # True

Multiple Assignment

Python lets you assign multiple variables at once, which keeps code concise.

python 
# Unpack into multiple variables
x, y = 3, 7
plot_x, plot_y = 0, 0

# Swap two variables (no temp variable needed)
x, y = y, x
print(x, y)   # 7 3

# Assign the same value to several variables
water = fertilizer = pesticide = 0

Constants Convention

Python has no built-in constant type, but by convention, variables intended to stay fixed are written in UPPER_SNAKE_CASE. This is a signal to other developers β€” and your future self β€” not to change the value.

python 
MAX_PLOTS = 64
BASE_GROWTH_RATE = 1.0
GRID_WIDTH = 8
GRID_HEIGHT = 8
SEASON_LENGTH_DAYS = 28

Practical Example: Farm Variables

Here's how you might model a crop plot in GrowBit using everything covered above:

python 
crop_name = "carrot"     # str  β€” what's planted
plot_x, plot_y = 2, 5   # int  β€” grid position
growth_days = 3          # int  β€” days since planting
is_mature = False        # bool β€” ready to harvest?
cost = 5                 # int  β€” seed cost in gold
sell_value = 15          # int  β€” harvest value in gold
water_level = 0.6        # float β€” 0.0 to 1.0

# Calculate profit margin
if is_mature:
    profit = sell_value - cost
    print(f"{crop_name} profit: {profit} gold")
else:
    remaining = 5 - growth_days   # carrot takes 5 days
    print(f"{crop_name} ready in {remaining} day(s).")

Every meaningful piece of game state β€” position, type, readiness, economics β€” is captured in a well-named variable with the right type. That's the foundation on which everything else is built.

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