Python Variables and Data Types: Numbers, Strings, and Booleans

Understanding Python Variables and Data Types

Variables are containers for storing data values. Python has several built-in data types that we'll explore in this lesson.

Creating Variables

In Python, you create a variable by assigning a value to it:

# Creating variables
name = "Alice"
age = 25
height = 5.6
is_student = True

print(name)    # Output: Alice
print(age)     # Output: 25
print(height)  # Output: 5.6
print(is_student)  # Output: True

Python Data Types

1. Numbers

Python has three numeric types:

# Integer (int)
age = 25
year = 2024

# Float (floating point number)
price = 19.99
temperature = -5.5

# Complex (complex numbers)
complex_num = 3 + 4j

print(type(age))         # 
print(type(price))       # 
print(type(complex_num)) # 

2. Strings (str)

Strings are sequences of characters:

# Different ways to create strings
name = "John"
message = 'Hello, World!'
multiline = """This is a
multiline string"""

# String operations
first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name
print(full_name)  # Output: John Doe

# String methods
text = "python programming"
print(text.upper())      # PYTHON PROGRAMMING
print(text.capitalize()) # Python programming
print(text.replace("python", "Python"))  # Python programming

3. Booleans (bool)

Booleans represent True or False values:

is_sunny = True
is_raining = False

# Boolean operations
print(is_sunny and is_raining)  # False
print(is_sunny or is_raining)   # True
print(not is_raining)           # True

Type Conversion

You can convert between different data types:

# Converting to string
age = 25
age_str = str(age)
print("I am " + age_str + " years old")

# Converting to integer
price_str = "19"
price_int = int(price_str)
print(price_int + 1)  # Output: 20

# Converting to float
score_str = "95.5"
score_float = float(score_str)
print(score_float)  # Output: 95.5

Variable Naming Rules

• Must start with a letter or underscore
• Can contain letters, numbers, and underscores
• Case-sensitive (age and Age are different)
• Cannot use Python keywords (if, for, while, etc.)

Practice Exercise

Create a program that:

1. Stores your personal information in variables
2. Performs calculations with numbers
3. Demonstrates string operations

# Personal information
name = "Your Name"
age = 20
height = 5.8
is_student = True

# Calculations
birth_year = 2024 - age
future_age = age + 10

# String operations
greeting = "Hello, my name is " + name
info = f"I am {age} years old and {height} feet tall"

print(greeting)
print(info)
print(f"I was born in {birth_year}")
print(f"In 10 years, I will be {future_age} years old")