python I want to set_index dataFrame with datetime

Question

poorList = [datetime.date(2016, 5, 2), 
            datetime.date(2016, 8, 26), 
            datetime.date(2016, 6, 9), 
            datetime.date(2016, 3, 4)]

dateForm.set_index(poorList)

then it was Error：

File "pandas\index.pyx", line 137, in pandas.index.IndexEngine.get_loc (pandas\index.c:4066) File "pandas\index.pyx", line 159, in pandas.index.IndexEngine.get_loc (pandas\index.c:3930) File "pandas\hashtable.pyx", line 675, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12408) File "pandas\hashtable.pyx", line 683, in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12359) KeyError: datetime.date(2016, 5, 2)

Please tell me how to do it ?

Answer 1

DataFrame.set_index() expects a column name or list of columns as an argument, so you should do:

dateForm['date'] = poorList
dateForm.set_index('date', inplace=True)

Answer 2

Another solutions is assign list converted to_datetime or DatetimeIndex:

poorList = [datetime.date(2016, 5, 2), 
            datetime.date(2016, 8, 26), 
            datetime.date(2016, 6, 9), 
            datetime.date(2016, 3, 4)]

dateForm.index = pd.DatetimeIndex(poorList)

print (dateForm.index)
DatetimeIndex(['2016-05-02', '2016-08-26', '2016-06-09', '2016-03-04'], 
dtype='datetime64[ns]', freq=None)

Solution with sample:

dateForm = pd.DataFrame({'A':[1,2,3,7],
                         'B':[4,5,6,8]})

print (dateForm)
   A  B
0  1  4
1  2  5
2  3  6
3  7  8

poorList = [datetime.date(2016, 5, 2), 
            datetime.date(2016, 8, 26), 
            datetime.date(2016, 6, 9), 
            datetime.date(2016, 3, 4)]

dateForm.index = pd.to_datetime(poorList)
print (dateForm)
            A  B
2016-05-02  1  4
2016-08-26  2  5
2016-06-09  3  6
2016-03-04  7  8

print (dateForm.index)
DatetimeIndex(['2016-05-02', '2016-08-26', '2016-06-09', '2016-03-04'], 
              dtype='datetime64[ns]', freq=None)

Answer 3

To generate an index with time stamps, you can use either the DatetimeIndex or Index constructor and pass in a list of datetime objects:

dateForm.set_index(pd.DatetimeIndex(poorList), inplace=True)  # Even pd.Index() works

Another way of doing would be to convert the list into an array as set_index accepts it's key as arrays and specify it's dtype accordingly.

dateForm.set_index(np.array(poorList, dtype='datetime64'), inplace=True)