I am using Datastream Web Service in Python and try to retrieve a time series of daily price changes (expression) for a single instrument or multiple instruments over a certain time horizon.
df=ds.get_data(tickers='S:NESN', fields='PCH#(X,1D)', start='-2Y', end='-0D', freq='W')
If I run this request, I receive the following error message:
Error - please check instruments and parameters (time series or static)
What am I doing wrong?
Thanks for your help.