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I have the following code where I'm trying to get the values in an array by the name I set.

import datetime
import numpy as np
import matplotlib.finance as finance
import matplotlib.mlab as mlab

def get_pxing(my_tickers):
    dt = np.dtype([('sym', np.str_, 6), ('adj_close', np.float32)])
    close_px = []
    for ticker in my_tickers:
    # a numpy record array with fields: date, open, high, low, close, volume, adj_close)
        fh = finance.fetch_historical_yahoo(ticker, startdate, enddate)
        r = mlab.csv2rec(fh)    
        fh.close()
        prices = np.array((ticker, r.adj_close), dtype=dt)
        close_px.append(prices)
    return close_px

enddate = startdate = datetime.date.today() - datetime.timedelta(1)

my_tickers = np.genfromtxt('./stocklist.csv', delimiter = ",", dtype=None, names=True)

data = get_pxing(my_tickers["ticker"])
print data

This works fine but if I try

print data['sym']

I get:

Traceback (most recent call last):
  File "stockyield.py", line 26, in <module>
    print data['sym']
TypeError: list indices must be integers, not str

Perhaps I've converted my array incorretly using the close_px.append, however, but I cannot figure out how to use the np.append as I always get an array mismatch.

My input csv file looks like:

ticker, holding
T, 100
F, 200

Any suggestions on best approach?

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data['sym'] would index a dictionary for an entry with key 'sym'. The data structure you have is a list. Figure out where the data you want is (perhaps by using data.index()) –  aestrivex Apr 5 at 14:31
 
get_pxing returns a list of arrays (close_px), not a numpy array. –  Warren Weckesser Apr 5 at 14:35

1 Answer

up vote 0 down vote

As the comments say, it seems you are appending a numpy array to a list of arrays. You really want to make a list of tuples, then convert the list of tuples into an array.

Try something like this (the changed lines have comments)

def get_pxing(my_tickers):
    dt = np.dtype([('sym', np.str_, 6), ('adj_close', np.float32)])
    close_px = []
    for ticker in my_tickers:
    # a numpy record array with fields: date, open, high, low, close, volume, adj_close)
        fh = finance.fetch_historical_yahoo(ticker, startdate, enddate)
        r = mlab.csv2rec(fh)    
        fh.close()
        prices = (ticker, r.adj_close)   # append a tuple to your list instead of an array
        close_px.append(prices)
    return np.array(close_px, dtype=dt)  # make the list of tuples into an array with dtype dt
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