How to generate powers of 10 with list comprehension or numpy functions?-CodePudding

I am generating this series of numbers using a for loop

[1.e-03 1.e-04 1.e-05 1.e-06 1.e-07 1.e-08 1.e-09 1.e-10 1.e-11 1.e-12]

This is the for loop:

alphas = np.zeros(10)
alphas[0] = 0.001
for i in range(1,10):    
    alphas[i] = alphas[i-1] * 0.1

My heart of hearts tells me this is not "pythonic", but my brain can't come up a list comprehension to build this.

I've tried numpy.linspace, arange, etc, but can't quite land where I need to. I wrote the for loop in 60 seconds, but am trying every time I write a for loop to think about how I could do it with a list comprehension.

CodePudding user response：

Think about what you want the range on: it's powers of 10

[10**x for x in range(-3, -13, -1)]

10.0**np.arange(-3, -13, -1)
# or
10.0**-np.arange(3, 13)

The numpy example uses a float 10.0 because in numpy,

Integers to negative integer powers are not allowed

Try it online

CodePudding user response：

Very similar answer to @Pranav, but personally I always find ascending ranges easier to read:

>>> [10 ** -k for k in range(3, 13)]
[0.001, 0.0001, 1e-05, 1e-06, 1e-07, 1e-08, 1e-09, 1e-10, 1e-11, 1e-12]

>>> np.power(10., -np.arange(3, 13))
array([1.e-03, 1.e-04, 1.e-05, 1.e-06, 1.e-07, 1.e-08, 1.e-09, 1.e-10,
       1.e-11, 1.e-12])