Change NaN values with returned value of API-CodePudding

I need to change the NaN values in one column with the returned value of an API. I already wrote a function that calls the function and returns a value but not I am not sure how to change the values now. Would I need to loop through the whole DataFrame or are there other solutions? The dataframe looks like this:

colname1	colname2	colname3
1	2	3
4	5	6
7	8	9
NaN	11	12

My function takes values 11 and 12, and gives as return 10 to input in df["colname1"] for the last row. My question is how I can loop through the whole DataFrame to solve all such instances.

CodePudding user response：

You can use apply. The best is to first subset the rows with NaNs to avoid requesting the API on the other values:

def api_func(a, b):
    return 10

# mask of the rows with NaN in colname1
m = df['colname1'].isna()

# output of API request
s = df.loc[m].apply(lambda r: api_func(r['colname2'], r['colname3']), axis=1)

# updating the column (in place)
df['colname1'].update(s)

output:

   colname1  colname2  colname3
0       1.0         2         3
1       4.0         5         6
2       7.0         8         9
3      10.0        11        12