Basics of Python

1. Variables

Variables store data.

name = "Arun"
age = 20
height = 5.8

Here:

• name stores text (string)
• age stores a whole number (integer)
• height stores a decimal number (float)

print(name)
print(age)

Output:

Arun
20

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2. Data Types

Common Python data types:

name = "Python"      # string
age = 25             # integer
price = 99.99        # float
is_active = True     # boolean

Check a type:

print(type(age))

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3. Input and Output

Getting input from the user:

name = input("Enter your name: ")
print("Hello", name)

Example:

Enter your name: Ravi
Hello Ravi

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4. Operators

Arithmetic

a = 10
b = 3

print(a + b)  # addition
print(a - b)  # subtraction
print(a * b)  # multiplication
print(a / b)  # division
print(a % b)  # remainder

Comparison

print(a > b)
print(a < b)
print(a == b)

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5. Conditional Statements (if)

Make decisions in code.

age = 18

if age >= 18:
    print("Adult")
else:
    print("Minor")

Multiple conditions:

marks = 75

if marks >= 90:
    print("A")
elif marks >= 70:
    print("B")
else:
    print("C")

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6. Loops

For Loop

for i in range(5):
    print(i)

Output:

0
1
2
3
4

While Loop

count = 1

while count <= 5:
    print(count)
    count += 1

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7. Lists

Store multiple values.

fruits = ["apple", "banana", "orange"]

print(fruits[0])

Add an item:

fruits.append("mango")

Loop through a list:

for fruit in fruits:
    print(fruit)

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8. Functions

Functions let you reuse code.

def greet(name):
    print("Hello", name)

greet("Kumar")

Return values:

def add(a, b):
    return a + b

result = add(5, 3)
print(result)

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9. Dictionariesv

Store data as key-value pairs.

student = {
    "name": "Arun",
    "age": 20,
    "city": "Chennai"
}

print(student["name"])

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10. Importing Modules

Use built-in Python libraries.

import math

print(math.sqrt(25))

Output:

5.0

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11. Error Handling

Prevent programs from crashing.

try:
    num = int(input("Enter number: "))
    print(num)
except ValueError:
    print("Please enter a valid number")

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12. A Complete Beginner Program

name = input("Enter your name: ")
age = int(input("Enter your age: "))

if age >= 18:
    print("Hello", name)
    print("You are eligible to vote.")
else:
    print("Hello", name)
    print("You are not eligible to vote.")