Python check if list in list of lists with numpy arrays

Question

I want to check if my query which is of type list is in the database (a list of lists). In the example below it is.

query = [np.array([[4,3],[6,4]]),5,2,1,5]

database = [ [np.array([[8,5],[2,1]]),5,3,1,9],
             [np.array([[4,3],[6,4]]),5,2,1,5],
             [np.array([[7,2],[6,4]]),0,0,8,5]]

I have tried this:

np.any([(query==data) for data in database])

However, I get the following error:

ValueError: The truth value of an array with more than one element is ambiguous. 
Use a.any() or a.all()

unutbu · Accepted Answer · 2019-08-18 12:43:18Z

1

Since np.array_equal can accept arrays or scalars, you could use it this way:

In [107]: any(all(np.array_equal(datum, q) for datum, q in zip(data, query)) for data in database)
Out[107]: True

If your scalars are floats, you may wish to use np.allclose instead of np.array_equal since testing for exact float equality is often not desireable:

In [108]: np.array_equal(0.1+0.2, 0.3)
Out[108]: False

In [109]: np.allclose(0.1+0.2, 0.3)
Out[109]: True

answered Aug 18, 2019 at 12:43

unutbu

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U13-Forward · Accepted Answer · 2019-08-18 11:04:15Z

1

Try this:

query = [i.tolist() if isinstance(i, np.ndarray) else i for i in query]
print(np.any([[i.tolist() if isinstance(i, np.ndarray) else i for i in data] == query for data in database]))

Output:

True

answered Aug 18, 2019 at 11:04

U13-Forward

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1 Comment

piccolo Over a year ago

This definitely works thanks. I'm wondering whether there's a simpler (less verbose) solution.

John · Accepted Answer · 2022-11-12 12:26:37Z

0

Here is a quick one-liner

np.in1d(["a","b"],["c","k","b"])

Returns

array([False,  True])

It checks if each value of the first list is in the second list and returns True or False for each.

Hope that helps.

edited Nov 12, 2022 at 12:26

answered Nov 12, 2022 at 11:54

John

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