In this tutorial, we will learn how to write a program to calculate the factorial of a number in Python. We will cover the basics of using a loop to compute the factorial.

The factorial of a non-negative integer n is the product of all positive integers less than or equal to n. It is denoted by n! and is calculated as n! = n × (n-1) × (n-2) × ... × 1. The factorial of 0 is 1.

The syntax to calculate the factorial in Python is:

```
def factorial(n):
result = 1
for i in range(1, n + 1):
result *= i
return result
```

We can use a loop to calculate the factorial of a number.

For example,

- Define a function named
`factorial`

that takes one parameter`n`

. - Initialize a variable
`result`

to 1. - Use a
`for`

loop to iterate from 1 to`n`

(inclusive). - Multiply
`result`

by the current number in the loop. - Return the
`result`

after the loop ends. - Call the
`factorial`

function with the desired number and print the result.

```
def factorial(n):
result = 1
for i in range(1, n + 1):
result *= i
return result
# Calculate the factorial of 5
print(factorial(5))
```

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