'Opens the CSV file containing the sentiment analysis
information for all represented stocks and places
it into a pandas DataFrame.'

def _open_sentiment_csv(self):

    sentiment_path = os.path.join(self.csv_dir, self.filename)
    sent_df = pd.read_csv(sentiment_path, parse_dates=True, header=0, index_col=0, names=('Date', 'Ticker', 'Sentiment'))
    if (self.start_date is not None):
        sent_df = sent_df[self.start_date.strftime('%Y-%m-%d'):]
    if (self.end_date is not None):
        sent_df = sent_df[:self.end_date.strftime('%Y-%m-%d')]
    if (self.tickers is not None):
        sent_df = sent_df[sent_df['Ticker'].isin(self.tickers)]
    return sent_df
