Python Variables in Plain English 📦

A variable is like a labeled box where you can put any value and use it as many times as you need!

🎯 What is a variable?

Picture this: you have a box with “age” written on the side. Put the number 16 inside. Now whenever you need someone’s age, just open that box!

# Create a variable
age = 16

# Use it
print(age)        # 16
print(age + 5)    # 21
print(age * 2)    # 32

✏️ How to create a variable

Very simple: name = value

name = 'Alex'
age = 20
height = 1.75
is_student = True

Important: The = sign does NOT mean “equals”! It means “assign this value.”

📝 Naming rules

✅ Allowed

name = 'Ivan'
user_age = 25
firstName = 'Maria'
count_2 = 10
_private = 'secret'

❌ Not allowed

2name = 'error'      # Cannot start with a digit
user-age = 25        # Cannot use a hyphen
first name = 'test'  # Cannot have a space
if = 5               # Cannot use a keyword

🔄 Changing a variable’s value

You can change a variable at any time!

score = 0
print(score)  # 0

score = 10
print(score)  # 10

score = score + 5
print(score)  # 15

# Short form
score += 5    # Same as: score = score + 5
print(score)  # 20

🎨 Variable types

Python figures out what you want to store automatically!

# String (text)
name = 'Anna'
city = "London"
message = '''Long text
spanning
multiple lines'''

# Integer
age = 18
year = 2026
temperature = -5

# Float (decimal)
height = 1.65
price = 99.99
pi = 3.14159

# Boolean
is_adult = True
has_license = False

🔍 Checking a variable’s type

name = 'Oleg'
age = 25
height = 1.80
is_student = True

print(type(name))       # <class 'str'>
print(type(age))        # <class 'int'>
print(type(height))     # <class 'float'>
print(type(is_student)) # <class 'bool'>

💡 Working with variables

Copying

x = 10
y = x     # y gets a COPY of x's value
y = 20    # Changing y does NOT affect x!

print(x)  # 10
print(y)  # 20

Swapping values

# The Pythonic way!
a = 5
b = 10

a, b = b, a  # Swap values

print(a)  # 10
print(b)  # 5

Multiple assignment

# Assign the same value to multiple variables
x = y = z = 0
print(x, y, z)  # 0 0 0

# Assign different values at once
name, age, city = 'Ivan', 20, 'Moscow'
print(name)  # Ivan
print(age)   # 20
print(city)  # Moscow

🎯 Common mistakes

Mistake 1: Using a variable before creating it

# ❌ Error!
print(name)  # NameError: name 'name' is not defined
name = 'Pete'

# ✅ Correct
name = 'Pete'
print(name)  # Create it first, then use it

Mistake 2: Quotes vs no quotes

name = 'Vasya'

print('name')  # Prints: name  (this is a string literal)
print(name)    # Prints: Vasya (this is the variable's value)

# With quotes — it's text
# Without quotes — it's a variable

Mistake 3: Case matters!

age = 16
Age = 20
AGE = 25

print(age)  # 16
print(Age)  # 20
print(AGE)  # 25

# These are THREE DIFFERENT variables!

Mistake 4: Non-ASCII variable names

# ⚠️ Technically works, but strongly discouraged
имя = 'Vasya'
print(имя)  # Vasya

# ✅ Better to use ASCII names
name = 'Vasya'
print(name)  # Vasya

💪 Best practices

1. Use meaningful names

# ❌ Bad
a = 16
x = 'London'
tmp = 1.75

# ✅ Good
age = 16
city = 'London'
height = 1.75

2. snake_case for variables

# ✅ Python convention
user_name = 'Ivan'
first_name = 'Maria'
total_score = 100

3. UPPER_CASE for constants

# Values that never change
MAX_SPEED = 120
PI = 3.14159
API_KEY = 'secret123'

🚀 Practical examples

Example 1: User survey

print('=== Survey ===')

name = input('Name: ')
age = int(input('Age: '))
city = input('City: ')
hobby = input('Hobby: ')

print(f'\n📝 Your details:')
print(f'Name: {name}')
print(f'Age: {age}')
print(f'City: {city}')
print(f'Hobby: {hobby}')

Example 2: Age calculator

current_year = 2026
birth_year = int(input('What year were you born? '))

age = current_year - birth_year

print(f'You are {age} years old')
print(f'In 10 years you will be {age + 10}')
print(f'5 years ago you were {age - 5}')

Example 3: Currency converter

# Exchange rates
usd_to_eur = 0.92
gbp_to_eur = 1.17

dollars = float(input('How many dollars do you have? '))
pounds = float(input('How many pounds do you have? '))

euros_from_usd = dollars * usd_to_eur
euros_from_gbp = pounds * gbp_to_eur
total_euros = euros_from_usd + euros_from_gbp

print(f'\nTotal in euros: €{total_euros:.2f}')

📋 Cheat sheet

# Create
variable = value

# Update
variable = new_value
variable += 5  # Add 5
variable -= 3  # Subtract 3
variable *= 2  # Multiply by 2
variable /= 4  # Divide by 4

# Check type
type(variable)

# Type conversions
str(123)     # '123'
int('456')   # 456
float('1.5') # 1.5
bool(1)      # True

🎓 Summary

• A variable = a named container for a value
• Created with name = value
• Can be changed at any time
• Names should be in English, using snake_case
• Python infers the data type automatically
• Use descriptive names!

Variables are the foundation of programming. They make your code flexible and readable! 💪