Geek asks and answers

How to output column index name in dataframe

                     Open     High    Low    Close   Volume      Adj Close
Date                        
1990-01-02 00:00:00  35.25   37.50   35.00   37.25   6555600     8.70
1990-01-03 00:00:00  38.00   38.00   37.50   37.50   7444400     8.76
1990-01-04 00:00:00  38.25   38.75   37.25   37.63   7928800     8.79
1990-01-05 00:00:00  37.75   38.25   37.00   37.75   4406400     8.82
1990-01-08 00:00:00  37.50   38.00   37.00   38.00   3643200     8.88

How can I get rid of the Date index name in the above dataframe? It should be on the same line as the names of the other columns, but not the problem that causes the problem.

thank

+2
source share
2 answers

Short answer: you cannot and do not understand why this can "cause problems." The name Date refers to a DataFrame index that is different from any of the columns. It is printed with this offset specifically so that you do not confuse it with the frame column. You would not slice a date with the DataFrame['Date']following:

>>> import numpy as np; import pandas; import datetime

>>> dfrm = pandas.DataFrame(np.random.rand(10,3), 
... columns=['A','B','C'], 
... index = pandas.Index(
... [datetime.date(2012,6,elem) for elem in range(1,11)],
... name="Date"))

>>> dfrm
                   A         B         C
Date                                    
2012-06-01  0.283724  0.863012  0.798891
2012-06-02  0.097231  0.277564  0.872306
2012-06-03  0.821461  0.499485  0.126441
2012-06-04  0.887782  0.389486  0.374118
2012-06-05  0.248065  0.032287  0.850939
2012-06-06  0.101917  0.121171  0.577643
2012-06-07  0.225278  0.161301  0.708996
2012-06-08  0.906042  0.828814  0.247564
2012-06-09  0.733363  0.924076  0.393353
2012-06-10  0.273837  0.318013  0.754807

>>> dfrm['Date']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/frame.py", line 1458, in __getitem__
    return self._get_item_cache(key)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/generic.py", line 294, in _get_item_cache
    values = self._data.get(item)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/internals.py", line 625, in get
    _, block = self._find_block(item)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/internals.py", line 715, in _find_block
    self._check_have(item)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/internals.py", line 722, in _check_have
    raise KeyError('no item named %s' % str(item))
KeyError: 'no item named Date'

Longer answer:

DataFrame, , , . :

>>> dfrm['Date'] = dfrm.index

>>> dfrm
                   A         B         C        Date
Date                                                
2012-06-01  0.283724  0.863012  0.798891  2012-06-01
2012-06-02  0.097231  0.277564  0.872306  2012-06-02
2012-06-03  0.821461  0.499485  0.126441  2012-06-03
2012-06-04  0.887782  0.389486  0.374118  2012-06-04
2012-06-05  0.248065  0.032287  0.850939  2012-06-05
2012-06-06  0.101917  0.121171  0.577643  2012-06-06
2012-06-07  0.225278  0.161301  0.708996  2012-06-07
2012-06-08  0.906042  0.828814  0.247564  2012-06-08
2012-06-09  0.733363  0.924076  0.393353  2012-06-09
2012-06-10  0.273837  0.318013  0.754807  2012-06-10

, :

>>> dfrm.reindex(pandas.Series(dfrm.index.values, name=''))
                   A         B         C        Date

2012-06-01  0.283724  0.863012  0.798891  2012-06-01
2012-06-02  0.097231  0.277564  0.872306  2012-06-02
2012-06-03  0.821461  0.499485  0.126441  2012-06-03
2012-06-04  0.887782  0.389486  0.374118  2012-06-04
2012-06-05  0.248065  0.032287  0.850939  2012-06-05
2012-06-06  0.101917  0.121171  0.577643  2012-06-06
2012-06-07  0.225278  0.161301  0.708996  2012-06-07
2012-06-08  0.906042  0.828814  0.247564  2012-06-08
2012-06-09  0.733363  0.924076  0.393353  2012-06-09
2012-06-10  0.273837  0.318013  0.754807  2012-06-10

. - - :

>>> dfrm.reset_index()

,

>>> dfrm.index = range(len(dfrm))

>>> dfrm
          A         B         C        Date
0  0.283724  0.863012  0.798891  2012-06-01
1  0.097231  0.277564  0.872306  2012-06-02
2  0.821461  0.499485  0.126441  2012-06-03
3  0.887782  0.389486  0.374118  2012-06-04
4  0.248065  0.032287  0.850939  2012-06-05
5  0.101917  0.121171  0.577643  2012-06-06
6  0.225278  0.161301  0.708996  2012-06-07
7  0.906042  0.828814  0.247564  2012-06-08
8  0.733363  0.924076  0.393353  2012-06-09
9  0.273837  0.318013  0.754807  2012-06-10

, :

>>> dfrm.ix[:,[-1]+range(len(dfrm.columns)-1)]
         Date         A         B         C
0  2012-06-01  0.283724  0.863012  0.798891
1  2012-06-02  0.097231  0.277564  0.872306
2  2012-06-03  0.821461  0.499485  0.126441
3  2012-06-04  0.887782  0.389486  0.374118
4  2012-06-05  0.248065  0.032287  0.850939
5  2012-06-06  0.101917  0.121171  0.577643
6  2012-06-07  0.225278  0.161301  0.708996
7  2012-06-08  0.906042  0.828814  0.247564
8  2012-06-09  0.733363  0.924076  0.393353
9  2012-06-10  0.273837  0.318013  0.754807

iPython script ( ), , Python.

###########
# Imports #
###########
import pandas
import datetime
import numpy as np
from dateutil import relativedelta
from pandas.io import data as pdata


############################################
# Functions to retrieve Yahoo finance data #
############################################

# Utility to get generic stock symbol data from Yahoo finance.
# Starts two days prior to present (or most recent business day)
# and goes back a specified number of days.
def getStockSymbolData(sym_list, end_date=datetime.date.today()+relativedelta.relativedelta(days=-1), num_dates = 30):

    dReader = pdata.DataReader
    start_date = end_date + relativedelta.relativedelta(days=-num_dates)
    return dict( (sym, dReader(sym, "yahoo", start=start_date, end=end_date)) for sym in sym_list )                     
###

# Utility function to get some AAPL data when needed
# for testing.
def getAAPL(end_date=datetime.date.today()+relativedelta.relativedelta(days=-1), num_dates = 30):

    dReader = pdata.DataReader
    return getStockSymbolData(['AAPL'], end_date=end_date, num_dates=num_dates)
###

:

#####
# Define a 'Stock' class that can hold simple info
# about a security, like SEDOL and CUSIP info. This
# is mainly for debugging things and quickly getting
# info for a single security.
class MyStock():

    def __init__(self, ticker='None', sedol='None', country='None'):
        self.ticker = ticker
        self.sedol=sedol
        self.country = country
    ###


    def getData(self, end_date=datetime.date.today()+relativedelta.relativedelta(days=-1), num_dates = 30):
        return pandas.DataFrame(getStockSymbolData([self.ticker], end_date=end_date, num_dates=num_dates)[self.ticker])
    ###


#####
# Make some default stock objects for common stocks.
AAPL = MyStock(ticker='AAPL', sedol='03783310', country='US')
SAP  = MyStock(ticker='SAP',  sedol='484628',   country='DE')
+8

reset_index, DataFrame ( , , ).

+10

More articles:


All Articles