df['product']=df['product'].fillna(0)
df['context']=df['context'].fillna(0)
df
df.fillna(0)
In [7]: df
Out[7]:
0 1
0 NaN NaN
1 -0.494375 0.570994
2 NaN NaN
3 1.876360 -0.229738
4 NaN NaN
In [8]: df.fillna(0)
Out[8]:
0 1
0 0.000000 0.000000
1 -0.494375 0.570994
2 0.000000 0.000000
3 1.876360 -0.229738
4 0.000000 0.000000
DataFrame.fillna()
mylist = [0 if x != x else x for x in mylist]