How to compute cumulative sum of previous N rows in pandas?

Question

I am working with pandas, but I don\'t have so much experience. I have the following DataFrame:

          A
0       NaN
1      0.00
2      0.00
3      3.33
4         


        

Answer 1

you might have to do it the hard way

B = []
i =0
m_lim = 11
while i=m_lim and i < len(A) -m_lim:
        B.append(sum(A[i-m_lim:i]))
    if i>= len(A) -m_lim:
      B.append(sum(A[i:]))
    i=i+1
df['B'] = B