如何切片pandas.DataFrame？

Question

Here's a pd.Dataframe.

index date  state
one   2000  Ohio
two   2012  Ohio

And I want df['state'] = 'California' where df['date'] == 2000 and df.index == one .

How can I do this?

Thanks for the help!

Answer 1

df.loc[df.state=='California' and df.date==2000 and df.index=='one', :]

Answer 2

Use if index is not column set new values by DataFrame.loc with conditions:

print (df.columns)
Index(['date', 'state'], dtype='object')

df.loc[(df['date'] == 2000) & (df.index == 'one'), 'state'] = 'California'
print (df)
       date       state
index                  
one    2000  California
two    2012        Ohio

If index is column select it by [] :

print (df.columns)
Index(['index', 'date', 'state'], dtype='object')

df.loc[(df['date'] == 2000) & (df['index'] == 'one'), 'state'] = 'California'
print (df)
  index  date       state
0   one  2000  California
1   two  2012        Ohio