# Factorial of a number in Python – Coderbyte Solution

### First Factorial

Factorial of a number in Python

Have the function FirstFactorial(num) take the num parameter being passed and return the factorial of it. For example: if num = 4, then your program should return (4 * 3 * 2 * 1) = 24.

For the test cases, the range will be between 1 and 18 and the input will always be an integer.

Input: 4
Output: 24

Input: 8
Output: 40320

#### Code:

Method1:

```#Using Recursion
def FirstFactorial(num):
# code goes here
if num==1:
return 1
else:
return num * FirstFactorial(num-1)

# keep this function call here
print(FirstFactorial(input()))```

This solution utilizes recursion to calculate the factorial of a given number (`num`). Here’s how it works:

1. The `FirstFactorial` function is defined, which takes a single parameter `num`.
2. Inside the function:
• The base case is checked: if `num` is equal to 1, then the factorial of 1 is 1, so the function returns 1.
• If the base case is not met (i.e., `num` is not 1), the function recursively calls itself with the argument `num-1`.
• Each recursive call decrements `num` by 1 until it reaches the base case (num equals 1).
3. When the base case is reached (num equals 1), the function starts returning values back up the call stack, multiplying `num` with the result of the recursive call (i.e., `num * FirstFactorial(num-1)`).
4. Finally, the result of the outermost function call (i.e., the factorial of the original input number) is printed.

Method2:

```def FirstFactorial(num):
# code goes here
f=1
for i in range(1,num+1):
f=f*i
return f
# keep this function call here
print(FirstFactorial(input()))```

This solution computes the factorial of a given number `num` using a simple iterative approach. Here’s how it works:

1. The `FirstFactorial` function is defined, which takes a single parameter `num`.
2. Inside the function:
• A variable `f` is initialized to 1. This variable will hold the factorial value.
• A `for` loop iterates from 1 to `num` (inclusive). For each iteration:
• The value of `f` is updated by multiplying it with the current value of `i`.
• After the loop completes, the final value of `f` represents the factorial of `num`.
3. The computed factorial value `f` is then returned by the function.
4. The function is called with `input()`, which takes user input from the console. However, note that `input()` returns a string, so the input should be cast to an integer for the function to work correctly.
5. Finally, the result of the `FirstFactorial` function call is printed.