# Python – math.comb() 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.comb()` method in Python is used to get the number of ways to choose k items from n items without repetition and without order. It basically evaluates to n! / (k! * (n – k)!) when k n. It is also known as binomial coefficient because it is equivalent to the coefficient of k-th term in polynomial expansion of the expression (1 + x)n.
This method is new in Python version 3.8.

Syntax: math.comb(n, k)

Parameters:
n: A non-negative integer
k: A non-negative integer

Returns: an integer value which represents the number of ways to choose k items from n items without repetition and without order.

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

 `# Python Program to explain math.comb() 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 without order``nCk ``=` `math.comb(n, k)``print``(nCk)`` ` `n ``=` `5``k ``=` `3`` ` `# Get the number of ways to choose``# k items from n items without``# repetition and without order``nCk ``=` `math.comb(n, k)``print``(nCk)`

Output:

```45
10
```

Code #2: When k > n

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

Output:

```0
```

Code #3: Use of `math.comb()` method to find coefficient of k-th term in binomial expansion of expression (1 + x)n

 `# Python Program to explain math.comb() method`` ` `# Importing math module``import` `math`` ` `n ``=` `5``k ``=` `2`` ` `# Find the coefficient of k-th``# term in the expansion of ``# expression (1 + x)^n``nCk ``=` `math.comb(n, k)``print``(nCk)`` ` `n ``=` `8``k ``=` `3`` ` `# Find the coefficient of k-th``# term in the expansion of ``# expression (1 + x)^n``nCk ``=` `math.comb(n, k)``print``(nCk)`

Output:

```10
56
```

Reference: Python math library

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