NumPy array initialization with tuple (fill with identical tuples)

Question

I would like to create an array which is filled with identical tuples initially, specifically with tuples of NaN. E.g.,

array([[(nan, nan), (nan, nan)],
       [(nan, nan), (nan, nan)],
       [(nan, nan), (nan, nan)]], dtype=object)

However, when using the array initialisations listed e.g. here with an iterable value as value for filling in array, python apparently tries to reshape that iterable into the new array rather than fill it with it:

np.full([3,2],(np.nan,np.nan,np.nan),dtype=tuple)
#ValueError: could not broadcast input array from shape (3) into shape (3,2)

np.fill does not work either, it requires a scalar.

Is it only possible to fill the array item by item?

Provide provide code in the question, instead of providing link, or provide an explicit link to the code itself — Shivam Jha
– Shivam Jha, Commented Sep 9, 2020 at 14:23
What do you actually intend to do with those tuples? The accepted answer didn't actually fill the array with tuples. It made a structured array, which displays elements as tuples. And when dealing with object arrays as you tried, there's a difference between 'identical tuples' and the 'same tuple'. — hpaulj
– hpaulj, Commented Sep 9, 2020 at 15:57
@hpaulj it is an initialisation for an array whose elements will contain maximum floating point value within an array of tuples of the same shape. So yes, it's identical, if I understand correctly and 'same' would mean reference to one single tuple. — Joce
– Joce, Commented Sep 10, 2020 at 6:16

yatu · Accepted Answer · 2020-09-09 14:23:48Z

3

You can, with the correct dtype. With 'f,f' you can initialise the array with tuples of floats; see Data type objects (dtype) for more.

np.full((3,2), np.nan, dtype='f,f')

array([[(nan, nan), (nan, nan)],
       [(nan, nan), (nan, nan)],
       [(nan, nan), (nan, nan)]], dtype=[('f0', '<f4'), ('f1', '<f4')])

answered Sep 9, 2020 at 14:23

yatu

88.6k12 gold badges93 silver badges148 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Joce Over a year ago

Thanks - it's probably a different issue, but then elements within the tuples are not np.nan anymore, A[0,0][0] is np.nan returns false? Although math.isnan returns true.

yatu Over a year ago

that is because np.nan!=np.nan (try it). You need to use np.isnan(A[0,0][0]) @joce

Joce Over a year ago

Thanks - I had seen syntax is np.nan elsewhere, but I realise now how wrong it is - means "is the same memory object".

Collectives™ on Stack Overflow

NumPy array initialization with tuple (fill with identical tuples)

1 Answer 1

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related