Project Euler is a website that lists a number of mathematical problems, which are perfect to be solved with NumPy. Let’s start the new year with Problem 1.

**1. Call the arange function**

Call the arange function in order to store all the integers from 1 to 1000 in an array.

# 1. Numbers 1 - 1000 a = numpy.arange(1, 1000) |

**2. Select the multiples of 3 or 5**

Select using the [] operator.

# 2. Select multiple of 3 or 5 a = a[(a % 3 == 0) | (a % 5 == 0)] print a[:10] |

This prints as expected

[ 3 5 6 9 10 12 15 18 20 21] |

**3. Sum the array elements**

Call the sum method on the NumPy array.

# 3. Sum the numbers print a.sum() |

Once again the code below in its entirety.

import numpy #Problem 1. #If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. #The sum of these multiples is 23. #Find the sum of all the multiples of 3 or 5 below 1000. # 1. Numbers 1 - 1000 a = numpy.arange(1, 1000) # 2. Select multiple of 3 or 5 a = a[(a % 3 == 0) | (a % 5 == 0)] print a[:10] # 3. Sum the numbers print a.sum() |

If you liked this post and are interested in NumPy check out NumPy Beginner’s Guide by yours truly.