Question

Say I have two series: a and b,

a = Series(None, index=['a','b','c'])
b = Series('lol', index=['j','k','l'])

I would like to store b as one of the elements of a,

a['a'] = b

but I get

ValueError: setting an array element with a sequence.

Is it possible to store a pandas series inside a pandas series? How can I do it? Thanks.

Answer 1

You can recast the dtype using the method astype:

In [11]: a = a.astype(object)

In [12]: a['a'] = b

In [13]: a
Out[13]: 
a    [lol, lol, lol]
b                NaN
c                NaN

Alternatively (to using astype) when contructing a you can force the dtype to be object:

In [14]: a = Series(None, index=['a','b','c'], dtype=object)

The reason you are getting this error is because float64, doesn’t allow a Series and similarly it doesn’t allow strings – try to set a['a'] = 'lol' and you’ll get a ValueError.

In [21]: a = Series(None, index=['a','b','c'])

In [22]: a.dtype
Out[22]: dtype('float64')

You can read more about type-casting in the docs.