Find last non-zero element's index in pandas series

Question

I\'d like to find the index of last non-zero element in pandas series. I can do it with a loop:

ilast = 0
for i in mySeries.index:
    if abs(mySeries[i]) > 0         


        

Answer 1

Just came up with a few solutions.

A couple of ways it with generator:

max(i for i in s.index if s[i] != 0) # will work only if index is sorted

and

next(i for i in s.index[::-1] if s[i] != 0)

which is quite readable and also relatively quick.

Through numpy's trip_zeros:

import numpy as np
np.trim_zeros(s, 'b').index[-1]

which is slower than both of the @DSM answers.

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Summary:

timeit np.trim_zeros(s, 'b').index[-1]
10000 loops, best of 3: 89.9 us per loop

timeit s[s != 0].index[-1]
10000 loops, best of 3: 68.5 us per loop

timeit next(i for i in s.index[::-1] if s[i] != 0)
10000 loops, best of 3: 19.4 us per loop

timeit max(i for i in s.index if s[i] != 0)
10000 loops, best of 3: 16.8 us per loop

timeit s.index[s.nonzero()[0][-1]]
100000 loops, best of 3: 1.94 us per loop