- Python Basic Programs
- Python Program Examples
- Python Print Hello World
- Python Get Input from User
- Python Add Two Numbers
- Add Subtract Multiply Divide
- Python Check Even or Odd
- Python Check Prime or Not
- Python Check Alphabet or Not
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- Python Check Leap Year or Not
- Check Reverse equal Original
- Check Positive Negative Zero
- Python Check Armstrong or Not
- Python Check Palindrome or Not
- Python Check Perfect Number
- Python Find Reverse of Number
- Python Count Digits in Number
- Python Add Digits of Number
- Sum of First and Last Digits
- Python Product of Mid Digits
- Sum of Squares of Digits
- Interchange Digits of Number
- Python Sum of n Numbers
- Python Print ASCII Values
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- Python Fahrenheit to Celsius
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- Python Display Calendar
- Python Days into Years, Weeks
- Find Largest of Two Number
- Find Largest of Three Number
- Python Print Fibonacci Series
- Generate Armstrong Numbers
- Python Make Simple Calculator
- Python Add Binary Numbers
- Binary Number Multiplication
- Python Mathematical Programs
- Find Sum of Natural Numbers
- Find Average of n Numbers
- Python Print Multiplication Table
- Print Table using Recursion
- Python Find Average Percentage
- Python Find Grade of Student
- Find Square Root of Number
- Python Print Prime Numbers
- Find Numbers Divisible by
- Python Find Factors of Number
- Python Find Factorial of a Number
- Python Find HCF & LCM
- Python Kilometres to Miles
- Python Find Area of Square
- Python Find Area of Rectangle
- Python Find Area of Triangle
- Python Find Area of Circle
- Python Find Perimeter of Square
- Find Perimeter of Rectangle
- Python Find Perimeter of Triangle
- Find Circumference of Circle
- Python Simple Interest
- Python Solve Quadratic Equation
- Python Different Set of Operations
- Python Display Powers of 2
- Python Find nCr & nPr
- Python Pattern Programs
- Python Print Pattern Programs
- Python Print Diamond Pattern
- Python Print Floyd's Triangle
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- Python List Programs
- Python Count Even/Odd in List
- Python Positive/Negative in List
- Python Even Numbers in List
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- Python Sum of Elements in List
- Sum of Odd/Even Numbers
- Python Element at Even Position
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- Python Search Element in List
- Python Largest Number in List
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- Python Second Largest in List
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- Python Insert Element in List
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- Python 1D Array Program
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- Remove Duplicates from List
- Python Reverse a List
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- Python Copy a List
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- Python Decimal to Binary
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- Python Decimal to Hexadecimal
- Python Binary to Decimal
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- Python Binary to Hexadecimal
- Python Octal to Decimal
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- Python Octal to Hexadecimal
- Python Hexadecimal to Decimal
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- Python Matrix Programs
- Python Add Two Matrices
- Python Subtract Two Matrices
- Python Transpose Matrix
- Python Multiply Matrices
- Python String Programs
- Python Print String
- Python Find Length of String
- Python Compare Two Strings
- Python Copy String
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- Python Reverse a String
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- Python Uppercase to Lowercase
- Python Lowercase to Uppercase
- Python Check Substring in String
- Python Count Character in String
- Count Repeated Characters
- Python Count Word in Sentence
- Python Count Each Vowels
- Python Capitalize Character
- Python Capitalize Word in String
- Python Smallest/Largest Word
- Remove Spaces from String
- Remove Duplicate Character
- Remove Vowels from String
- Remove Punctuation from String
- Python Remove Word in String
- Python Remove Duplicate Words
- WhiteSpace to Hyphens
- Replace Vowels with Character
- Replace Character in String
- Python Sort String in Alphabetical
- Sort Word in Alphabetical Order
- Extract Number from String
- Python Check Anagram Strings
- Python File Programs
- Python Read a File
- Python Write to File
- Python Append Text to File
- Python Copy Files
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- Python Counts Characters in File
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- Python File Content in Reverse
- Python Lines Contains String
- Python Delete Line from File
- Python Capitalize Word in File
- Python Replace Text in File
- Replace Specific Line in File
- Python Find Size of File
- Python List Files in Directory
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- Python Reverse a Tuple
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- Python bytes to String
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- Generate Random Numbers
- Python Print Address of Variable
- Python Print Date and Time
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- All Test List
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# Python Program to Find Area of Circle

In this article, we've created some programs in Python to find and print area of a circle using its radius value entered by user at run-time. Here are the list of programs:

- Find Area of Circle without Function
- Find Area of Circle using User-defined
**Function** - Using
**Class**

### Formula to Find Area of Circle

To find area of a circle with given value of radius, use following formula:

a = 3πr^{2}= 3*3.14*r*r

Here **a** indicates to *area value*, **r** indicates to *radius value* of circle.

**Note - **The value of **π** is **3.14**.

## Find Area of Circle

This program receives radius of circle as input from user at run-time, then find and prints its area. The question
is **write a Python program to compute area of a circle.** Here is its answer:

print("Enter the Radius of Circle: ") r = float(input()) a = 3*3.14*r*r print("\nArea = ", a)

Here is its sample run:

Now supply the input say **5** as radius of circle, press `ENTER`

key to find and print the area
of circle based on given radius value as shown in the snapshot given below:

### Find Area of Circle using Diameter Input

The question is, **write a Python program to calculate area of circle if diameter is inputted.** The answer to this question is given below:

print("Enter the Diameter of Circle: ", end="") d = float(input()) r = d/2 a = 3*3.14*r*r print("\nArea = ", a)

Here is its sample run with user input **10** as diameter:

**Note - **Diameter is the length of line passing through the center of circle, from one side to other.

**Note - **Radius is the length of line from center of circle to any outside edge.

**Note - **Diameter to Radius relation is, __Radius's length is one-half of Diameter's Length__. Or __Diameter is Double the length of Radius__

## Find Area of Circle using Function

This program does the same job as of very first program of this article. The only difference is, its approach. That is,
this program uses user-defined function named **areaOfCircle()**, that find and returns area based on the radius
passed as its argument.

def areaOfCircle(rad): ar = 3*3.14*rad*rad return ar print("Enter the Radius of Circle: ", end="") r = float(input()) a = areaOfCircle(r) print("\nArea = ", a)

Here is its sample run with user input, **10** as radius of circle:

## Find Area of Circle using Class

This program uses class and object, an object-oriented feature of Python to find and print area of a circle.

class CodesCracker: def areaOfCircle(self, rad): ar = 3*3.14*rad*rad return ar print("Enter the Radius of Circle: ", end="") r = float(input()) CCobj = CodesCracker() a = CCobj.areaOfCircle(r) print("\nArea = ", a)

This program produces the same output as of previous program. In this program, using the statement,
**CCobj = CodesCracker()**, all properties of class **CodesCracker** gets assigned to this object (**CCobj**).
Now we can use this object to access the member function (**areaOfCircle()**) to find area of circle in similar
way as done in previous program using user-defined function.

#### Same Program in Other Languages

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