CODEWITHSUNDEEP
pythonpython-2.7pandas
Pavan
Pavan

Reputation: 239

How to compare two cells in a given DataFrame in pandas Python 2.7

This is the code that I am using. 

from datetime import date, datetime, timedelta
import pandas_datareader.data as web
todays_date = date.today()
n = 30
date_n_days_ago = date.today() - timedelta(days=n)
stock_data = web.DataReader('ACC.NS', 'yahoo', date_n_days_ago, todays_date)
stock_data = stock_data[stock_data.Volume != 0].tail(20)
stock_data = stock_data[['Adj Close']]

Now I go to ipython termnal and type:

stock_data['Adj Close'].iloc[[19]] > stock_data['Adj Close'].iloc[[0]]

then the output I get is: 

Date

2016-02-18    True

But when I go to my IPython (or my editor Spyder) and code:

if stock_data['Adj Close'].iloc[[19]] > stock_data['Adj Close'].iloc[[0]]:
    print " greater"

the output I get is:

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

MY DOUBT: Why does this happen ?

Presently I have found a workaround code:

adj_close_list = stock_data.values.T.tolist()
if adj_close_list[0][19] > adj_close_list[0][0]:
    print "greater"
else:
    print "less"

Is there any way I can do away with this workaround and directly compare two cells in a DataFrame?

Upvotes: 3

Views: 963

Answers (1)

Mike Müller
Mike Müller

Reputation: 85562

Remove the extra []:

if stock_data['Adj Close'].iloc[19] > stock_data['Adj Close'].iloc[0]:
    print('greater')
else:
    print('less')

This gives you a float, i.e. a cell:

>>> stock_data['Adj Close'].iloc[19]
1256.3499999999999

But this gives you a series:

>>> stock_data['Adj Close'].iloc[[19]]
Date
2016-02-18    1.256E+03
Name: Adj Close, dtype: float64

When you compare two series you get another series, which you cannot use in an if statement directly.

Upvotes: 1

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