Return the index of the last element in a pandas series

Question

I want to return the index of the last element of a pandas series. I've been looking at SO entries, but none of the solutions worked.

I tried

 last_element=df.index[-1]

and

 last_element=df[-1].index

Could you post the error messages (if you get any), or the "wrong" results you are getting using the methods mentioned in your question? The first method seems to work well for me. — UJIN, Oct 23 '19 at 08:35

Kshitij Saxena · Answer 1 · 2019-10-23T07:59:17.883

1

Try this:

df.reset_index(inplace=True)
df[-1].index

edited Oct 23 '19 at 07:59

answered Oct 23 '19 at 07:58

Kshitij Saxena

930
8
19

Try creating a `pd.Series` like this: `s = pd.Series({0:1}); s.append(pd.Series({0:2}))` – Kshitij Saxena Oct 23 '19 at 08:05
If your series has an index, then `df[-1].index` should work. Show the head of your series or any error that you're getting. – Kshitij Saxena Oct 23 '19 at 08:08

tyb9900 · Accepted Answer · 2019-10-23T08:08:12.680

0

Try

 df.last_valid_index()

Works for me.

Edit:

To store last element you can use iloc

last_element = df.iloc[-1:]

edited Oct 23 '19 at 08:08

answered Oct 23 '19 at 07:55

tyb9900

214
2
11

1

[`DataFrame.last_valid_index`](http://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.last_valid_index.html) - Return index for last non-NA/null value. - it is somethibng else like need OP – jezrael Oct 23 '19 at 07:58
1

@cheesus - exactly, answer is really bad for general data with mising values, not use it. – jezrael Oct 23 '19 at 08:16
all is wrong, OP need `I want to return the index of the last element of a pandas series. ` – jezrael Oct 23 '19 at 08:47
1

yes, in my case there won't be a nan value at the last row ever :) – cheesus Oct 23 '19 at 09:37

score 0 · Answer 3 · answered Oct 23 '19 at 08:00

Call the tail() function with the argument 1 (you want one element from the end, or the last element), and index[0] on this, which returns the index of the element.

df.tail(1).index[0]

Check out this post for more details: index And this one for info about tail: tail function

score 0 · Answer 4 · answered Oct 23 '19 at 08:11

I know you said it didn't work for you, but really the way I usually retrieve the last index is with df.index[-1]. I tested it and it works both for DataFrames and Series:

df = pd.DataFrame(data={'col1':[1,4,5,3,3,5,6,7,8,9,5,4,2], 
                        'col2':[1,4,5,3,3,5,6,7,8,9,5,4,2]})

df.index[-1]
>> 12

And

df = pd.Series([1,4,5,3,3,5,6,7,8,9,5,4,2])

df.index[-1]
>> 12

If this doesn't work, can you tell us more about the errors you are getting?

Return the index of the last element in a pandas series

4 Answers4