def standard_deviation(data, period):
catch_errors.check_for_period_error(data, period)<EOL>stds = [np.std(data[idx+<NUM_LIT:1>-period:idx+<NUM_LIT:1>], ddof=<NUM_LIT:1>) for idx in range(period-<NUM_LIT:1>, len(data))]<EOL>stds = fill_for_noncomputable_vals(data, stds)<EOL>return stds<EOL>
Standard Deviation.

Formula:
std = sqrt(avg(abs(x - avg(x))^2))