Pandas dataframe, extract consecutive rows of a column to a list

Question

I have, what seems to be a simple problem, but I cannot find an answer....

Assuming a pandas dataframe such as:

df = pd.DataFrame({"a": [1,2,3,4,5], "b": [4,5,6,7,8]})

In column b , I would like to extract a list containing the values of n consecutive rows starting x rows from the last row.

Assuming n=3 and x=1 , I would like to get:

list = [7,6,5] or list = [5, 6, 7]

I cannot figure out how to slice the relevant segment of dataframe to achieve this.

Any ideas? Thank you ! Baka

Answer 1

your_list = list(df['b'][-x-1:-x-n-1:-1])

Answer 2

I think in your case you can use

forward direction list(df['b'][x:(x+n)]) ==>> [5,6,7]

or

backward direction list(df['b'][-(x)-1:-(x+n)-1:-1]) ==> [7,6,5]

Answer 3

You can just do this:

n = -4
x = -1
lst = df.b.iloc[n:x].tolist()
print(lst)

Output:

[5, 6, 7]