How to calculate differences between consecutive rows in pandas data frame?

Question

I\'ve got a data frame, df, with three columns: count_a, count_b and date; the counts are floats, and the dates are conse

Answer 1

diff should give the desired result:

>>> df.diff()
count_a  count_b
2015-01-01      NaN      NaN
2015-01-02    38465      NaN
2015-01-03    36714      NaN
2015-01-04    35137      NaN
2015-01-05    35864      NaN
....
2015-02-07   142390    25552
2015-02-08   126768    22835
2015-02-09   122324    21485