将多索引系列附加到熊猫中的空系列

Question

I take a multi-indexed pandas series named 'dat' and try to append it to an empty series named 's'. This is how 'dat' looks like:

a = [['bar', 'bar', 'foo', 'foo'],['one', 'two', 'one', 'two']]
t = list(zip(*a))
ind = pd.MultiIndex.from_tuples(t, names=['first', 'second'])
dat = pd.Series(randn(4), index=ind)

Out[1]: 
first  second
bar    one      -1.361606
       two      -0.108458
foo    one      -0.691175
       two      -0.830161
dtype: float64

Now, when I append it to the empty Series 's' it returns this:

s = pd.Series()
s = s.append(dat)
Out[2]: 
(bar, one)   -1.361606
(bar, two)   -0.108458
(foo, one)   -0.691175
(foo, two)   -0.830161
dtype: float64

How can I recover the original form?

Answer 1

This was a bug fixed in 0.14.0 (coming next week), see here: http://pandas-docs.github.io/pandas-docs-travis/whatsnew.html#whatsnew-0140-api (the set_index section).

You can get the pre-release here: https://github.com/pydata/pandas/releases