I want to create an n-by-2 NumPy array, and then test whether it contains a particular 1-by-2 array (i.e. whether it contains a particular row).
Here is my code:
x = np.array([0, 1])
y = np.array([2, 3])
z = np.vstack((x, y))
if x in z:
print "Yes"
But this gives me the error:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
Please could somebody explain this to me? Thanks!
You may be using an older version of numpy since on 1.10 this does work;
>>> x = np.array([0, 1])
>>> y = np.array([2, 3])
>>> z = np.vstack((x, y))
>>> x in z
True
>>> np.__version__
'1.10.1'
That said, it does not do what you want:
>>> z
array([[0, 0],
[0, 0]])
>>> x
array([0, 1])
>>> x in z
True
as commented out here, x in z is equivalent of (x == z).any(), not kind of row search that you want.
To implement what you need, you may do:
>>> (z == x).all(axis=1).any()
True
