Python - Fundamentals

In here, I'm gonna tell you how to use variables in python. We shall see how to name a variable and assign values to them.

How to name a Variable ?

Firstly a variable is nothing but a reference to an object or value throughout the program. They act as reference to a memory where the value is stored.

There are certain rules to name them.

• Must begin with a letter (a-z, A-Z) or an underscore (_).
• After the first character, letters, digits (0-9), or underscores can be followed.
• Variable names are case-sensitive. For ex, myName and myname are entirely different variables.
• Should not use Python reserved words as variable names For ex: class, def, for, while.

So, in python the operator = is used for assigning values to variables.

# Assigning integer value
age = 18
print(age)

18

# Assigning string value
name = "Arif"
print(name)

Arif

# Assigning float value (float means decimal value)
height = 2.5
print(height)

2.5

# Assigning boolean value (rfrs to true/false)
is_student = True
print(is_student)

True

Varible Types

Python is a typed lang, we needn't declare the type of a variable when assigning a value to it. The type is inferred by its own.

name = "Abys"
print(name)
print(type(name))

Abys
<class 'str'>

or we can also define the type by,

name = "Abys"
type(name)

str

age = 18
type(age)

int

That's the basic.

I've been asked to complete some questions on my own, lemme discuss those with you guys.
It's much easier to learn right...?

1. Create a variable named name and assign your name to it. Then print the value of the variable.

name = "Abys"
print(name)
print(type(name))

Abys
<class 'str'>

2. Create a variable age and assign your age to it. Later, reassign the variable with a new value and print the new value.

age=17
print("Present age:",age)
age= 18
print(age)

Present age: 17
18

and here if we want the type;

print(type(age))
<class 'int'>

3. Assign the values 5, 10, and 15 to three variables a, b, and c in a single line. Print their values.

a,b,c = 5,10,15
print(a,b,c)

5 10 15

if we wanna add them we get,

print(a+b+c)

30

4. Swap the values of two variables x and y without using a third variable. Print their values before and after swapping.

x,y = 5,25
print(x,y)
print(x-y)
x,y = 25,5
print(x,y)
print(x-y)

5 25
-20
25 5
20

they've asked just to print the swapped values, it's me u did extra stuffs.

Before the next qn we ought to know what is constants...

What are Constants ?

In Python, constants are those values that are not meant to change. By convention, they are typically written in capital letters with underscores separating the words.
However, in python constants can also be changed.

5. Define constants PI with appropriate values and print them.

PI=3.14159
print(f"{PI:.3f}")

3.142

6. Write a program that calculates the area of a circle using the constant PI and a variable radius. Print the area.

PI=3.14
radius=7
r=radius
area=PI*r**2 # r**2 refers to r pow 2
print("Area of circle is",area)

Area of circle is 153.86

7. Define constants for the length and width of a rectangle. Calculate and print the area.

L,B = 5,15
area = L*B
print("Area of rect is ",area)

Area of rect is  75

These were the qns I worked out. Hope it is clear.
Thank you, All...

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