Variable,Constant and Literals Declaration in Python

Python Variables, Constants, and Literals

🔹 What is a Variable?

A variable is an identifier used to store a value in a program. In Python, a variable's type and value can change at runtime, making Python a dynamically typed language.

Key features of Python variables:

• Type is determined by the assigned value
• Same variable can store different data types at different times
• Memory allocation occurs automatically
• Python supports multiple assignments in one statement

✔ Variable Declaration Syntax

identifier = value              # Single assignment
x, y, z = 10, 20, 30            # Multiple assignment
a, b = 10, 20
print(a + b)

✔ Example: Input Using Variables

a, b = input("Enter first number: "), input("Enter second number: ")

print(a + b)          # "10" + "20" → "1020"
print(int(a) + int(b))   # 10 + 20 → 30
print(int(a + b))        # "1020" → 1020
print(int(a) + float(b))

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🔹 Naming Convention for Variables

Rules for naming variables:

• Must start with a letter (a–z or A–Z) or underscore (_)
• No spaces allowed
• Cannot use Python keywords (if, for, while, class, etc.)
• Use lowercase letters as per Python naming standards

Valid Examples:

name, age, total_amount, _count

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🔹 What is a Constant?

A constant is a special type of identifier whose value cannot be changed during program execution. Python does not have true constants, but developers use:

• Tuples (immutable data type)
• Uppercase variable names (naming convention)

✔ Example of Constant Using Tuple

constants = (3.14, 2.2, "https://www.shivaconceptsolution.com")

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🔹 What are Literals?

A literal is the actual value assigned to a variable or constant. Examples include numbers, strings, characters, and boolean values.

✔ Examples of Literals

a = 2          # integer literal
b = 3.14       # float literal
print("hello") # string literal

print(10 + 20)             # 10, 20 are integer literals
print("hello" + "world")   # string literals

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📝 Program: Reverse a Five-Digit Number (Without Loop)

num = 45123

a = num % 10     # 3
num = num // 10  # 4512

b = num % 10     # 2
num = num // 10  # 451

c = num % 10     # 1
num = num // 10  # 45

d = num % 10     # 5
e = num // 10    # 4

result = a*10000 + b*1000 + c*100 + d*10 + e
print(result)

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📚 ASSIGNMENT PROGRAMS

1️⃣ WAP to calculate the total salary of an employee

Given:

• basic = 12000
• ta = 400
• da = 200
• comm = 500
• pf = -500
• hra = 300
• leave = 3

✔ Solution Code

name = input("Enter name: ")
basic = float(input("Enter basic salary: "))
ta = float(input("Enter TA: "))
da = float(input("Enter DA: "))
comm = float(input("Enter Commission: "))
pf = float(input("Enter PF: "))
hra = float(input("Enter HRA: "))
lv = float(input("Enter number of leave days: "))

ctc = basic + ta + da + comm + hra + pf
print("CTC of employee is", ctc)

tsal = basic + ta + da + comm + hra
lvded = (tsal/30) * lv

gsal = tsal - lvded - pf
print("Gross Salary is", gsal)
print("Leave Deduction:", lvded, "PF Deduction:", pf)

# Writing into a file
f = open("salaryslip.doc", "w")
f.write("CTC (Annual): " + str(12*ctc))
f.write("\nName: " + name)
f.write("\nGross Salary: " + str(gsal))
f.write("\nLeave Deduction: {0}, PF Deduction: {1}".format(lvded, pf))
f.close()

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2️⃣ WAP to calculate electricity bill

up = float(input("Enter unit price: "))
cons = float(input("Enter total consumption: "))
load = float(input("Enter extra load unit: "))

bill = up * cons + 2 * (up * load)

print("Total bill is", bill)
print("Consumption without load:", up * cons)
print("Extra load consumption:", 2 * (up * load))

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3️⃣ WAP to calculate Simple Interest (SI)

Rate and Time are constant; Principal is entered by user.

4️⃣ WAP to calculate area of Triangle, Circle, and Rectangle

5️⃣ WAP to convert temperature from Celsius to Fahrenheit