Python Programma per trovare il fattoriale di un numero

The sections below show four ways to compute a factorial in Python — a for loop, an if-else version, recursion, and math.factorial() — plus the underlying algorithm and applications.

Fattoriale di un numero utilizzando il ciclo for

Let us take up the example of Python code that takes a positive integer as input to determine the factorial of positive integers. In the following code, the loop begins with one, and then it multiplies by each number that precedes the actual number whose factorial is to be determined.

Le seguenti Python code illustrates the factorial function using a loop.

Python codice:

print ("Input a number")
factorialIP = int (input ())
ffactor23 = 1
for j in range (1, factorialIP+1):
   ffactor23 = ffactor23 * j
print ("The factorial of the number is “, ffactor23)

Produzione:

Input a number
4
The factorial of the number is 24

Quanto sopra Python program takes the input of positive numbers only, and it does not have a check of negative numbers in it. In this program, the factor is 1 when j is equal to 1. When j is 2, the factor is multiplied with 2, and it will do the action till j comes at 4 to arrive at 24.

Fattoriale di un numero utilizzando l'istruzione IF…else

Le seguenti Python code illustrates the factorial function using a function. Unlike the loop version, this program also checks for negative numbers before computing the factorial.

Nel precedente Python code, the check for negative numbers was not applied, making the factorial function incomplete and prone to deliver an error message if negative numbers are given as an input.

In the given code, the loop begins with one and multiplies by each preceding number, and the function also validates the input for negative numbers.

Python codice:

print("Enter a number for the purpose of determining factorial")
factorialIP = int(input())
def factorial(factorialIP):
   if factorialIP < 0:
     print ('Factorial does not exist')
     factor=0
     return factor
   elif factorialIP == 0:
     factor=1
     return factor
     print(factor)
   else:
     factor = 1
     for j in range (1, factorialIP+1):
       factor = factor * j
     return factor
  print ("The factorial of the number is ", factorial(factorialIP))

Produzione:

1) Enter a number to determine factorial
   -4
   Factorial does not exist
   The factorial of the number is 0

2) Enter a number to determine factorial
   4
   Factorial does not exist
   The factorial of the number is 24

Questo Python program accepts positive numbers and adds a check for negative numbers using the if and else statement, correctly returning 24 for an input of 4.

Fattoriale di un numero utilizzando la ricorsione

Le seguenti Python code illustrates the factorial function using recursion. In this example, a recursive function that takes a positive integer as input determines the factorial number.

Python codice:

print("Enter a number for the purpose of determining factorial")
def factorial(num2):
  if num2 < 0:
    return 'Factorial does not exist'
  elif num2 == 0:
     return 1
  else:
     return num2 * factorial(num2-1)
number1 = int(input())
print("The factorial of the number is",factorial(number1))

Produzione:

Enter a number for the purpose of determining factorial
4
The factorial of the number is 24

The recursion can be explained as a concept wherein the function invoked in the Python module can call itself again and again. It runs until the Python condition present in the module is satisfied, wherein the function invoked is passed with a value.

Nel sopra Python program, the function def factorial keeps calling itself recursively until and unless the number reaches zero. Once the number reaches zero, it initializes the number as 1, ending the recursion.

Factorial of a Number using math.factorial()

Le seguenti Python code illustrates the factorial function using math.factorial(), which can be used by importing the math module.

This function does not accept negative integers, and it throws a value error when float numbers are provided.

Python codice:

print("Enter a number for computing factorial")
import math
number1 = int(input())
print("The factorial is as computed comes out to be ")
print(math.factorial(number1))

Produzione:

Enter a number for computing factorial
4
The factorial, as computed, comes out to be 24

Algoritmo per il programma fattoriale in Python

Facciamo un esempio che illustra il concetto di fattoriale.

For determination of factorial 5, follow these steps:

5! = 5 x (5-1) x (5-2) x (5-3) x (5-4)
5! =120

Ecco, 5! è espresso come 120.

Il diagramma seguente aiuta a comprendere l'algoritmo di calcolo del fattoriale e, in questo caso, prendiamo un esempio di fattoriale 4!

Algoritmo con esempio pittorico di fattoriale 4!

Applicazione del Fattoriale in Python

Il fattoriale di un numero ha un ampio livello di applicazioni in matematica. Ecco importanti applicazioni di Python:

• Python helps in computation, followed with print factorial in faster and more efficient terms than other available programming languages.
• Migliori Python code is easily understandable and can be replicated across different platforms, and the factorial Python program can be incorporated in several mathematical model-building assignments.

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