Calculating difference between two rows in Python / Pandas

Question

In python, how can I reference previous row and calculate something against it? Specifically, I am working with dataframes in pandas - I have a da

Answer 1

To calculate difference of one column. Here is what you can do.

df=
      A      B
0     10     56
1     45     48
2     26     48
3     32     65

We want to compute row difference in A only and want to consider the rows which are less than 15.

df['A_dif'] = df['A'].diff()
df=
          A      B      A_dif
    0     10     56      Nan
    1     45     48      35
    2     26     48      19
    3     32     65      6
df = df[df['A_dif']<15]

df=
          A      B      A_dif
    0     10     56      Nan
    3     32     65      6