'IntegerArray' object has no attribute 'T'

[bnaul]

In our case this arose via .cumsum():

pd.Series([0, 1], dtype='int64').cumsum()
0    0
1    1
dtype: int64

pd.Series([0, 1], dtype='Int64').cumsum()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-31-2ebc3e3cf698> in <module>
----> 1 pd.Series([0, 1], dtype='Int64').cumsum()
...

~/model/.venv/lib/python3.7/site-packages/pandas/core/generic.py in na_accum_func(blk_values)
  11324                 np.putmask(result, mask, mask_b)
  11325             else:
> 11326                 result = accum_func(blk_values.T, axis)
  11327
  11328             # transpose back for ndarray, not for EA

AttributeError: 'IntegerArray' object has no attribute 'T'

But it's also true that just calling .values.T on a regular int array works (just a no-op), whereas on an Int64 array it does not. Same is true for

Any reason not to just add a no-op .T on the base ExtensionArray class..? cc @TomAugspurger in case you have an opinion 🙂

[TomAugspurger]

In the past we've been hesitant to add useless methods to EAs simply because ndarrays have them. I'm not sure about adding it here.

[bnaul]

Makes sense; surely .cumsum() is not useless though 🙂. Would the right approach then be to have a separate implementation of that...?

[jorisvandenbossche]

cumsum is indeed useful, but should be implemented specifically for EAs probably, without requiring T.
There is an open PR related to this (#28509), but didn't check the status of it.

[jbrockmendel]

In the past we've been hesitant to add useless methods to EAs simply because ndarrays have them

This statement is technically correct (the best kind of correct), but there is not at all consensus that "T" is useless. This is just one more in a large pile of things that could be made easier.

[TomAugspurger]

As I said, it’s useless on its own for EAs. It’s potential use comes from writing code that works with both EAs and ndarrays.

[jbrockmendel]

the example from the OP works on master, could use test

update: it loses dtype

[mzeitlin11]

Closing in favor of #28385