Change Series inplace in DataFrame after applying function on it

Use loc:

wanted_data.loc[:, 'age'] = wanted_data.age.apply(lambda x: x + 1)

I would suggest wanted_data['age']= wanted_data['age'].apply(lambda x: x+1),then save file as wanted_data.to_csv(fname,index=False), where "fname" is the name of a file to be updated.