Python Program - Find Factorial of a Number


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The factorial of a positive integer is the multiplication of all positive integer less than or equal to that number.

$$factorial$$ $$of$$ $$number$$ $$n$$ = $$n! = n(n-1)(n-2)...1$$

For Example:

$$5! = 5\times4\times3\times2\times1 = 120$$

$$4! = 4\times3\times2\times1 = 24$$

Example: Using Recursive method

In the below example, a recursive function called factorial() is used to calculate factorial of a number.

def factorial(x):
  if x == 0 or x ==1:
    return 1
  else:
    return x*factorial(x-1)

print("10! = ", factorial(10))
print("6! = ", factorial(6))

Output

10! =  3628800
6! =  720

Example: Using Iterative method

The factorial of a number can also be calculated using iterative method.

def factorial(x):
  final = 1
  for i in range(x,1,-1):
    final = final * i
  return final

print("10! = ", factorial(10))
print("6! = ", factorial(6))

Output

10! =  3628800
6! =  720

Example: Using Short-hand If-else method (Ternary operator)

In the below example, the factorial of a number is calculated using short-hand if-else method.

def factorial(x):
  y = 1 if (x == 0 or x ==1) else x * factorial(x-1)
  return y

print("10! = ", factorial(10))
print("6! = ", factorial(6))

Output

10! =  3628800
6! =  720




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