Chapter 2 : Variables and Data Types

A variable is a name given to a memory location in a program.
For example

a=30
b=”Harry”
c=71.22

Variable – Container to store a value.
Keywords – Reserved words in Python.

Identifiers – class/function/variable name.

Data Types:

Primarily there are the following data types in Python:

  • Integers
  • Floating point numbers
  • Strings
  • Booleans
  • None

Python is a fantastic language that automatically identifies the type of data for us.

a = 71    
#Identifies a as class <int>

b = 88.44  
#Identifies b as class<float>


name = “Harry”  
#Identifies name as class<Str>

Rules for defining a variable name:

 (Also applicable to other identifiers)

  • A variable name can contain alphabets, digits, and underscore.
  • A variable name can only start with an alphabet and underscore.
  • A variable can’t start with a digit.
  • No white space is allowed to be used inside a variable name.

Examples of few valid variable names:

Harry, harry, one8, _akki, aakash, harry_bro, etc.

Operators in Python

The following are some common operators in Python:

  1. Arithmetic Operators (+, -, *, /, etc.)
  2. Assignment Operators (=, +=, -=, etc.)
  3. Comparison Operators (==, >=, <=, >, <, !=, etc.)
  4. Logical Operators (and, or, not)

type() function and Typecasting

type function is used to find the data type of a given variable in Python.

a = 31

type(a)                      #class<int>

b = “31”

type(b)                      #class<str>

A number can be converted into a string and vice versa (if possible)

There are many functions to convert one data type into another.

Str(31)           # ”31” Integer to string conversion

int(“32”)       # 32 String to int conversion

float(32)       #32.0 Integer to float conversion

… and so on

Here “31” is a string literal and 31 is a numeric literal.

input() function

This function allows the user to take input from the keyboard as a string.

a = input(“Enter name”)
#if a is “harry”, the user entered harry

Note: The output of the input function is always a string even if the number is entered by the user.

Suppose if a user enters 34 then this 34 will automatically convert to “34” string literal.

Chapter 2 – Practice Set

  1. Write a Python program to add two numbers.
  2. Write a Python program to find the remainder when a number is divided by Z(Integer).
  3. Check the type of the variable assigned using the input() function.
  4. Use a comparison operator to find out whether a given variable a is greater than b or not. (Take a=34 and b=80)
  5. Write a Python program to find the average of two numbers entered by the user.
  6. Write a Python program to calculate the square of a number entered by the user.