Module 2: Variables & Data Types

In this module, we will learn how to store data in computer memory using variables and explore the different types of data we can use in Python.

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2.1 Variables

A Variable is a container or a box used to store data in a computer's memory.

• Analogy: Think of jars in a kitchen. You might label one jar "sugar" and another "salt". In coding, we label variables to store numbers, names, or other values.

# Creating variables
age = 22
name = "Sai Kumar"

print(age)
print(name)

In this code, age is a variable name, and 22 is the value stored inside it.

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2.2 Naming Rules

When naming variables in Python, you must follow these rules:

1. A variable name must start with a letter (a-z, A-Z) or an underscore (_).
2. A variable name cannot start with a number (e.g., 1name is invalid, but name1 is valid).
3. A variable name can only contain letters, numbers, and underscores. Special characters (like @, $, %, &) are not allowed.
4. Python is Case-Sensitive. This means age and Age are two different variables.
5. You cannot use reserved keywords (like if, else, while, for, print) as variable names.

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2.3 Integer

An Integer is a whole number (positive, negative, or zero) without any decimal points.

students_count = 50
temperature = -5
zero_value = 0

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2.4 Float

A Float is a number that contains a decimal point.

pi = 3.14
price = 99.99
height = 5.8

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2.5 String

A String is a sequence of characters or text. Strings must be wrapped in double quotes ("...") or single quotes ('...').

channel_name = "Think IT Telugu"
message = 'Welcome to Python'

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2.6 Boolean

A Boolean represents only one of two values: True or False.

is_coding_easy = True
has_laptop = False

Note: In Python, True and False must always start with capital letters.

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2.7 Type Function

You can check the data type of any variable using the built-in type() function.

x = 100
y = 10.5
z = "Python"
is_active = True

print(type(x))         # Output: <class 'int'>
print(type(y))         # Output: <class 'float'>
print(type(z))         # Output: <class 'str'>
print(type(is_active)) # Output: <class 'bool'>

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2.8 Type Conversion

Converting one data type into another is called Type Conversion or Type Casting.

# Converting Float to Integer
price = 99.99
integer_price = int(price)
print(integer_price) # Output: 99 (decimal part is removed)

# Converting Integer to Float
age = 22
float_age = float(age)
print(float_age) # Output: 22.0

# Converting Number to String
score = 100
str_score = str(score)
print(type(str_score)) # Output: <class 'str'>

# Converting String to Integer (string must contain only digits)
num_str = "45"
num = int(num_str)
print(num + 5) # Output: 50

:::caution Warning If you try to convert a text string (like "hello") into an integer, Python will show a ValueError. :::