Get Stock Symbols

This function gets the list of symbols for stocks from indices and/or sectors.

This program gets the stock symbols of a user-defined index (NASDAQ, NYSE, AMEX, OTCBB, LSE) and/or sector. The data is retrieved from http://www.eoddata.com/ and from Yahoo Finance.

For example:
- get_stock_symbols('NASDAQ') : gets all stock symbols from NASDAQ
- get_stock_symbols('biotechnology') : gets all biotechnology stock symbols from all above indices.
-get_stock_symbols('NASDAQ',biotechnology') : gets all symbols for all biotechnology companies listed in NASDAQ.

Note:
- get_stock_symbols('515') : equivalent to the get_stock_symbols('biotechnology'), since biotechnology has the sector code 515. Run get_stock_symbols('list') for a list of sector codes and descriptions.