Mastering_variables_in_python notes

What is a Variable?

A variable is a named container used to store data in memory.

Example:

x = 2
y = 3
z = x + y

Here:

x stores value 2
y stores value 3
z stores result 5

Think of it like:

name = "tk"

name is the label, "tk" is the value stored.

Why do we need variables?

Without variables, we would need to manually write values again and again.

Example without variable:

print(5000 + 2000)
print((5000 + 2000) * 12)

With variable:

salary = 5000
bonus = 2000

total = salary + bonus
yearly = total * 12

print(total)
print(yearly)
Benefits:
Reusability
Easy updates
Better readability
Stores dynamic user input
Helps in calculations
Python automatically assigns datatype

Python is dynamically typed, meaning you don't need to mention datatype manually.

x = 10
name = "tk"
price = 10.5

Python automatically understands the datatype.

Basic Data Types in Python
1. Integer (int)

Stores whole numbers.

x = 10
print(type(x))

Output:

<class 'int'>
2. Float (float)

Stores decimal numbers.

a = 5.6
print(type(a))

Output:

<class 'float'>
3. String (str)

Stores text data.

b = "tk"
print(type(b))

Output:

<class 'str'>
4. Boolean (bool)

Stores True or False values.

c = True
print(type(c))

Output:

<class 'bool'>
Internally:
True = 1
False = 0

Example:

val1 = True
val2 = False

print(val1 - val2)

Output:

1

Example:

print(val1 * val2)

Output:

0
5. Complex (complex)

Used for imaginary numbers.

d = 7 + 2j
print(type(d))

Output:

<class 'complex'>
Real part:
print(d.real)

Output:

7.0
Imaginary part:
print(d.imag)

Output:

2.0

Yes — .real and .imag return float values.

Variable Naming Rules / Characteristics

Python variables are case-sensitive

name = "tk"
Name = "python"

Both are different variables.

Valid variable names:
age = 25
user_name = "tk"
salary1 = 50000
Invalid variable names:
1name = "tk"   ❌
user-name = "tk" ❌
class = "python" ❌
How to check datatype?

Use type()

x = 100
print(type(x))
Your Practice Set
1. Fibonacci Series
n = 10
a, b = 0, 1

for i in range(n):
    print(a)
    a, b = b, a + b

Output:

0
1
1
2
3
5
8
13
21
34
2. Palindrome

Palindrome means same forward and backward.

Example: madam, 121

word = input("Enter value: ")

if word == word[::-1]:
    print("Palindrome")
else:
    print("Not Palindrome")
Quick Interview Answer

What is variable?
A variable is a container that stores data values.

Why required?
To store data temporarily and reuse it during program execution.