idxmax
and argmax
will return the position of the maximal value or the first position if the maximal value occurs more than once.
use idxmax
on df.A.ne('a')
df.A.ne('a').idxmax()
3
or the numpy
equivalent
(df.A.values != 'a').argmax()
3
However, if A
has already been sorted, then we can use searchsorted
df.A.searchsorted('a', side="right")
array([3])
Or the numpy
equivalent
df.A.values.searchsorted('a', side="right")
3