replacing values in a whole array

Question

I would like to ask how I can change the values in a whole NumPy array.

For example I want to change every value which is < 1e-15 to be equal to 1e-15.

Answer 1

Assuming you mean a numpy array, and it's pointed to by a variable a:

np.fmax(a, 1e-15, a)

This finds the maximum of the two values given as the first two arguments (a and 1e-15) on a per-element basis, and writes the result back to the array given as the third argument, a.

I had a hard time finding the official docs for this function, but I found this.