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Python – math.perm() method
• Last Updated : 23 Jan, 2020

Math module in Python contains a number of mathematical operations, which can be performed with ease using the module. `math.perm()` method in Python is used to get the number of ways to choose k items from n items without repetition and with order. It Evaluates to n! / (n – k)! when k <= n and evaluates to 0 when k > n.
This method is new in Python version 3.8.

Syntax: math.perm(n, k = None)

Parameters:
n: A non-negative integer
k: A non-negative integer. If k is not specified, it defaults to None

Returns: an integer value which represents the number of ways to choose k items from n items without repetition and with order. If k is none, method returns n!.

Code #1: Use of `math.perm()` method

 `# Python Program to explain math.perm() method`` ` `# Importing math module``import` `math`` ` `n ``=` `10``k ``=` `2`` ` `# Get the number of ways to choose``# k items from n items without``# repetition and with order``nPk ``=` `math.perm(n, k)``print``(nPk)`` ` `n ``=` `5``k ``=` `3`` ` `# Get the number of ways to choose``# k items from n items without``# repetition and with order``nPk ``=` `math.perm(n, k)``print``(nPk)`
Output:
```90
60
```

Code #2: When k > n

 `# Python Program to explain math.perm() method`` ` `# Importing math module``import` `math`` ` `# When k > n ``# math.perm(n, k) returns 0.``n ``=` `3``k ``=` `5`` ` `# Get the number of ways to choose``# k items from n items without``# repetition and with order``nPk ``=` `math.perm(n, k)``print``(nPk)`
Output:
```0
```

Code #3: If k is not specified

 `# Python Program to explain math.perm() method`` ` `# Importing math module``import` `math`` ` `# When k is not specified``# It defaults to n and ``# math.perm(n, k) returns n ! n = 5`` ` `nPk ``=` `math.perm(n)``print``(nPk)`
Output:
```120
```

Reference: Python math library

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