Numerical Computing with Python

Getting the percentage change of the closing price

Next, we want to calculate the change of the closing price with regard to the previous day's close. The pct_change() function in Pandas makes this task very easy:

import numpy as np# Calculate percentage change versus the previous closestock_df["Close_change"] = stock_df["Close"].pct_change()# Since the DataFrame contain multiple companies' stock data, # the first record in the "Close_change" should be changed to# NaN in order to prevent referencing the price of incorrect company.stock_df.loc[stock_df["Date"]=="2017-01-03", "Close_change"] = np.NaNstock_df.head()