Selecting first element of a series

I have an series object that contains multiple series (341 in this case):

I need to select only first element of each series. For example if I have series:

0 68 -0.22
  86 2.54
1 73 -0.10
  88 0.57
2 74 -2.18
  89 -0.10

I need to get something that would look like this:

 0 68 -0.22
 1 73 -0.10 
 2 74 -2.18

and so on.

For empty series I need to ger series number and Nan,or 0:

336 0 0
337 0 0 

Thanks a lot!

>Solution :

What you want is unclear. Maybe you can try:

out = pd.concat({x.name: x.iloc[[0]] if not x.empty
                 else pd.Series(0) for x in sr})
print(out)

# Output
0    68   -0.22
1    73   -0.10
2    74   -2.18
341  0     0.00
dtype: float64