pandas replace nan

data["Gender"].fillna("No Gender", inplace = True) 

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

df['product']=df['product'].fillna(0)
df['context']=df['context'].fillna(0)
df

df['DataFrame Column'] = df['DataFrame Column'].fillna(0)

df.fillna(0)

df.replace(np.nan,0)

pandas.DataFrame.fillna(0)