How to check if an object is an np.array()?

Question

I'm trying to build a code that checks whether a given object is an np.array() in python.

if isinstance(obj,np.array()) doesn't seem to work.

I would truly appreciate any help.

np.ndarray, not np.array(): https://stackoverflow.com/a/36783987/483620 — Benjamin, Dec 11 '19 at 06:17

score 16 · Answer 1 · answered Dec 11 '19 at 06:26

16

isinstance(obj, numpy.ndarray) may work

answered Dec 11 '19 at 06:26

Kani

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Alen S Thomas · Answer 2 · 2019-12-11T06:33:31.980

4

You could compare the type of the object being passed to the checking function with 'np.ndarray' to check if the given object is indeed an np.ndarray

The sample code snippet for the same should look something like this :

if isinstance(obj,np.ndarray):
    # proceed -> is an np array
else
    # Not an np.ndarray

edited Dec 11 '19 at 06:33

answered Dec 11 '19 at 06:25

Alen S Thomas

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`isinstance` is the proper check in almost every case. This code will fail if `value` is an instance of a subclass of `numpy.ndarray`. – Perkins Dec 11 '19 at 06:30
Thank you so much for the clarification, sir. – Alen S Thomas Dec 11 '19 at 06:33

score 2 · Answer 3 · answered Dec 11 '19 at 06:26

2

Below code seems to work. Use numpy.ndarray.

import numpy as np

l = [1,2,3,4]

l_arr = np.array(l)

if isinstance(l_arr, np.ndarray):
    print("Type is np.array")
else:
    print("Type is not np.array")

Output:

Type is np.array

answered Dec 11 '19 at 06:26

Jay

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score 0 · Answer 4 · answered Dec 11 '19 at 06:28

The type of what numpy.array returns is numpy.ndarray. You can determine that in the repl by calling type(numpy.array([])). Note that this trick works even for things where the raw class is not publicly accessible. It's generally better to use the direct reference, but storing the return from type(someobj) for later comparison does have its place.

How to check if an object is an np.array()?

4 Answers4