Forward fill all except last value in python pandas dataframe

Question

I have a dataframe in pandas with several columns I want to forward fill the values for. At the moment I\'m doing:

columns = [\'a\', \'b\', \'c\']
for column in          


        

Answer 1

You can use last_valid_index in a lambda function to just ffill up to that point.

df = pd.DataFrame({
    'A': [1, None, None, None], 
    'B': [1, 2, None, None], 
    'C': [1, None, 3, None], 
    'D': [1, None, None, 4]})

>>> df
    A   B   C   D
0   1   1   1   1
1 NaN   2 NaN NaN
2 NaN NaN   3 NaN
3 NaN NaN NaN   4

>>> df.apply(lambda series: series.loc[:series.last_valid_index()].ffill())
    A   B   C  D
0   1   1   1  1
1 NaN   2   1  1
2 NaN NaN   3  1
3 NaN NaN NaN  4