过滤numpy浮点数组中的整数

Question

Is there any built in function to discard integer and keep only float number in numpy .

import numpy as np

input = np.array([0.0, 0.01, 1.0, 2.0, 2.001, 2.002])

desired_ouput = some_function(input)
# Expected ouput
# desired_output = np.array([0.01, 2.001, 2.002])

Answer 1

Mask with whether each element is equal to it as an integer.

arr = np.array([0.0, 0.01, 1.0, 2.0, 2.001, 2.002])
out = arr[arr != arr.astype(int)]
#np.array([0.01, 2.001, 2.002])

Answer 2

I don't think so. My approach would be

import numpy as np
a = np.array([0.0, 0.01, 1.0, 2.0, 2.001, 2.002])
mask = np.isclose(a, a.astype(int))

print(a[~mask])
#[ 0.01   2.001  2.002]

Answer 3

I know of no in-built function. But you can create one yourself:

import numpy as np

A = np.array([0.0, 0.01, 1.0, 2.0, 2.001, 2.002])

def remove_ints(arr):
    return arr[~(arr == arr.astype(int))]

res = remove_ints(A)

array([ 0.01 ,  2.001,  2.002])

Aside, you should not use a built-in class such as input as a variable name.

Answer 4

I've always used np.equal with np.mod :

>>> A[~np.equal(np.mod(A, 1), 0)]
array([0.01 , 2.001, 2.002])

Answer 5

If you do not have to much data (short list), maybe do not need numpy :

>>> i = [0.0, 0.01, 1.0, 2.0, 2.001, 2.002]
>>> a=[j for j in i if not j.is_integer()]
>>> a
['0.01', '2.001', '2.002']

Otherwise see Joe Iddon answer

Answer 6

I don't know any builtin for this but you can filter those floats using:

filter(lambda x: int(str(x).split('.')[1]) != 0, input)

The lambda expression here checks if the decimal places are zero which I interpret as the number being an int.

Answer 7

I had a similar question a while back: Numpy: Check if float array contains whole numbers . The simplest way to mask fractions that I am currently aware of is

mask = ((input % 1) != 0)

You can then apply the mask directly with

output = input[mask]

It bothered me that there is no built-in function to determine the integerness of a float quickly, so I wrote a ufunc that you can download from github and compile if you're interested:

from isint_ufunc import isint

output = input[~isint(input)]

I'll see if the numpy community wants to consider adding something like that to the core library. The question seems to come up often enough to justify it.