Question

I keep getting the same ValueError for the following code and I am having a hard time understanding why the error is being generated. It is my understanding that this error is generated when the wrong value is passed into a function, however, I do not really understand what this error is telling me. I’ve spent time searching online and in the docs, but I am unable to understand what I am doing wrong. Simply, why is this error being generated?

My code:

import datetime
import ystockquote

def new_time(n):
    fmt = "%Y%m%d"
    end_date1 = datetime.datetime.strptime(n, fmt)
    sixty_day = datetime.timedelta(days=60)
    start_date  = end_date1 - sixty_day
    start_date1 = str(start_date)
    start_date2 = start_date1[:4] + start_date1[5:7] + start_date1[8:10]
    return start_date2

def average_atr():
    print "Enter your stock symbol: "
    symbol      = raw_input(" ")
    print "Enter the end date in (YYYYMMDD) format: "
    end_date    = raw_input(" ")
    start_date  = new_time(end_date)
    initial_list = ystockquote.get_historical_prices('symbol', 'start_date', 'end_date')

def start():
    average_atr()

start()

This is the relevant code for ystockquote:

def get_historical_prices(symbol, start_date, end_date):
    """
    Get historical prices for the given ticker symbol.
    Date format is 'YYYYMMDD'

    Returns a nested list.
    """
    url = 'http://ichart.yahoo.com/table.csv?s=%s&' % symbol + \
          'd=%s&' % str(int(end_date[4:6]) - 1) + \
          'e=%s&' % str(int(end_date[6:8])) + \
          'f=%s&' % str(int(end_date[0:4])) + \
          'g=d&' + \
          'a=%s&' % str(int(start_date[4:6]) - 1) + \
          'b=%s&' % str(int(start_date[6:8])) + \
          'c=%s&' % str(int(start_date[0:4])) + \
          'ignore=.csv'
    days = urllib.urlopen(url).readlines()
    data = [day[:-2].split(',') for day in days]
    return data

Please note that the ystockquote code above is not the complete code.

Answer 1

In the function average_atr(), change the following line:

initial_list = ystockquote.get_historical_prices('symbol', 'start_date', 'end_date')

to:

initial_list = ystockquote.get_historical_prices(symbol, start_date, end_date)

In your current version, instead of passing the variables into ystockquote.get_historical_prices(), you are passing literal strings with the variable names. This is resulting in str(int(end_date[4:6]) - 1) with the variable end_date having the value 'end_date', and 'end_date'[4:6] is 'da'.