Pandas Fill consecutive null values with range of values between the first non null value before and after

Question

I have a dataframe where I would like to fill null values in a dataframe following two conditions

Condition 1: value after NaN (in this example 10) > value before NaN (7.5)

2.75
7.5
NaN
NaN
NaN
10

Equally increments from 7.5 to 10. So it would be like

2.75
7.5
8.125
8.75
9.375
10

PS: The increment is calculated as following (10-7.5/4) = 0.625

Condition 2: Value after NaN is < = value before Nan

2.75
10
NaN
NaN
NaN
7.5

Forward fill NaN values

2.75
10
10
10
10
7.5

Answer 1

If you are targeting this to do for a series, you can use:

df['Col'].fillna(df['Col'].interpolate().cummax())

For a dataframe:

df.fillna(df.interpolate().cummax())

---

Showing for a dataframe for con1 and cond 2( can be replicated for a series too )

print(df1)

     Col   Col1
0   2.75   2.75
1   7.50  10.00
2    NaN    NaN
3    NaN    NaN
4    NaN    NaN
5  10.00   7.50

---

print(df1.fillna(df1.interpolate().cummax()))
      Col   Col1
0   2.750   2.75
1   7.500  10.00
2   8.125  10.00
3   8.750  10.00
4   9.375  10.00
5  10.000   7.50