Two dataframes merged

[Ecniv]

Ok. Managed to get the index back and find the original row via the index. However it is still not doing it (still erroring) so I must still be doing it wrong.... any ideas (I have a headache now)
Final loop is now :

for i,r in checkout.iterrows():
    ind = -1
    f = cleaned[cleaned['atime'].isnull()]
    if f is not None:
        f = f[f['date']==r['date']]
    if f is not None:
        f = f[f['dtime']<r['atime']]
    if f is not None:
        cleaned.iloc[f.index[0]]['atime','arrival','cost']=r['atime','arrival','cost']