I need copy the value "a" lower and next I would like that the value of "b" will be also copied lower so many times until it encounters another value etc until the end of column 1

I tried to iterate through the rows and add conditions, unfortunately I wasn't get the result as I want. My dataframe looks like:

Result as I want:

CodePudding user response：

Use pandas.fillna with method=ffill:

When used on a column, this replaces the NaN values in a given row with non-NAN values preceding the row.

import pandas as pd 

data = pd.DataFrame({"col1": [1, None, 2, None, None, 3, None, 4, 5, None, None]})

data["col1"] = data["col1"].fillna(method="ffill")

print(data)

Output:

    col1
0    1.0
1    1.0
2    2.0
3    2.0
4    2.0
5    3.0
6    3.0
7    4.0
8    5.0
9    5.0
10   5.0

OR

Use pandas.ffill which works similar to above solution and looks more clean. Both the methods mentioned so far allows in place replacement of values.

Using ffill method: df['col1'].ffill(inplace=True).