# Find total number of non-decreasing numbers with n digits in Python

In this tutorial, we’re going to learn how to find the total number of non-decreasing numbers with n digits in Python using the NumPy library. But first, we need to understand what a non-decreasing number is. A non-decreasing number is a number in which every digit (other than the first digit) is equal to or greater than its previous digit.

Also, we need to understand the utility of NumPy. NumPy is a special library in Python that can be implemented to use various mathematical functions, multi-dimensional arrays, etc. We need to explicitly import the NumPy library in Python using the ‘import’ command.

Let’s first check how to import NumPy library in Python:

`import numpy as np;`

## Finding the total number of non-decreasing numbers in Python

```import numpy as np;

def count(n) :
c=np.zeros((n+1,10));
for i in range(10):
c[0][i] = 1;
for i in range(1,n+1):
c[i][9]=1;
for i in range(1,n+1):
for j in range(8,-1,-1):
c[i][j]=c[i-1][j]+c[i][j+1];
result=int(c[n][0]);
return result;

n=input("Enter number of digits:");
no=int(n);
print("Total no. of non-decreasing digits is ",count(no))

```

In this program, we are evaluating each of the numbers between a specified range and checking for the condition of the non-decreasing number. If the condition is satisfied, we’re counting the same. After executing the above code, we’ll find the total number of non-decreasing numbers with any number of digits.

Output generated will be:

```Enter no. of digits: 3
Total no. of non-decreasing digits is 220```