Conditionally create Json line level nodes

Question

I'm a newb to Python. I piece-meal a bit of Python code which uses pandas to read an Excel spreadsheet which contains one sheet for sales order header records, and another for sales order lines. The code probably can be written more efficiently, and it simply creates a Json output file.

At this point, I can throw in a couple of header rows into the Excel, and 1 or more line rows. The output is I'll get two Json files with specific header details, but both will have the same line records. I'd like to enhance the code to run a reference lookup between header and lines, then create the lines in the Json which below to a specific header orderid. Can anyone point me to some reference code which would allow a lookup to a data frame before traversing the records and building the Json string?

Thanks much!