How to change value for rows that meet specific conditions in pandas?

Question

I want to change the name in the name column to default for only rows that meet a specific condition ( name == None and weight == 1 ). As you can see weight can be 10, but I do not want to change the names for weights of 10. Here is a small example dataframe:

post   name  weight  response
blah1  None       1       yes
blah2  None      10        no
blah3  Annie      1       yes

How can I achieve this in a simple way?

Answer 1

快速，坚固，强大的熊猫式解决方案：

df.loc[(df.name == None) & (df.weight == 1), 'name'] = 'defaut'

Answer 2

You can update the dataframe with a filled in version of the 'name' column.

df.update(df.name[df.weight.eq(1)].fillna('default'))

df

    post     name  weight response
0  blah1  default       1      yes
1  blah2     None      10       no
2  blah3    Annie       1      yes

Answer 3

np.where((df['name'] == 'None') & (df['weight'] == 1), 'default', df['name'])