Series / DataFrame constructors inconsistent with data=None and dtype

[TomAugspurger]

The series constructed below should (I think) be a special case of the DataFrame example, but they differ.

In [4]: pd.DataFrame(None, index=[1, 2, 3], columns=['a'], dtype=int)
Out[4]:
    a
1 NaN
2 NaN
3 NaN

In [5]: pd.Series(None, index=[1, 2, 3], dtype=int)
Out[5]:
1    0
2    0
3    0
dtype: int64

I don't know which makes more sense.

[WillAyd]

Kind of nuanced but I'd side with the DF constructor here

[TomAugspurger]

Interesting, I was going to go with the Series one, since dtype=int is an explicit request from the user, whereas data is implicit. Though neither is especially intuitive.

Perhaps raising is the best action here :) We still allow the implicitly reindexing if we force the user to do Series(0, index=[1, 2, 3], dtype=int).

[WillAyd]

Yea raising is a good option if there’s a general way of doing it. Either way is ambiguous

[TomAugspurger]

Also, apparently the output of DataFrame(None, index=[1, 2], columns=['a'], dtype=object) is object, so the dtype= is only sometimes ignored.