Python for Finance

Chapter 4
Usually, there are two ways to retrieve data:
• Manually download data from a specific location and then write a Python
program to retrieve and process it
• Use the functions contained in various Python modules, such as the function
called quotes_historical_yahoo_ohlc() in the matplotlib.finance
submodule
For both methods, there are some advantages and disadvantages. The main
advantage of the first method is that we know where to get our data. In addition,
since we write our own programs to download and process data, the logic of those
programs is clearer. The advantage of the second method is that it is quick and
convenient to retrieve data. In a sense, users don't even have to know from where to
retrievethe data and the structure of the original datasets. The disadvantage is that the
functions used might change. This might cause certain problems. For example, the old
version of quotes_historical_yahoo_ohlc() is quotes_historical_yahoo().
In order to retrieve useful information from the preceding sources, two submodules
could be used: pandas_datareader.data and matplotlib.financial. To find out
functions included in pandas_datareader.data, the dir() function is applied:
From the preceding output, it seems that we have eight functions related
to YahooFinance, such as YahooDailyReader(), YahooActionReader(),
YahooOptions(), YahooQuotesReader(), get_components_yahoo(), get_data_
yahoo(), get_data_yahoo_actions(), and get_quote_yahoo(). Actually, we
could use theDataReader() function as well.Similarly, a few functions are available
for retrieving data from Google, FRED, and from Prof. French's Data Library.
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