Python Programming On Win32

Building Views with Arrays

So far we’ve seen examples of passing numbers, strings, and Python objects back and forth between Python and VB. Now we’ll develop some more kinds of views and look at passing around arrays of data at a time. This is a real time saver and can simplify the preceding code in several places.

Many financial reports take the form of a 2D grid or spreadsheet. What’s needed is a generic solution for getting a Python list of lists into such a grid. In the last chapter we showed a number of BookSet methods for getting a list of accounts, the details of an account and so on. For example, getAccountDetails returns a list of tuples of (transaction number, date, comment, amount, runningTotal). This is effectively a matrix with five columns but an unknown number of rows. You need to expose this the usual way in COMBookSet, but then access the entire matrix from VB. The Python COM framework automatically converts lists (or lists of lists, or lists of tuples) into arrays that can be accessed in VB.

We’ve created a new form, frmAccountView, which can be given the name of an account as a string. This has a Microsoft FlexGrid control called grdTable. Here’s the UpdateView method that fetches and displays the data:

Public Sub UpdateView() Dim table As Variant Dim rows As Integer, cols As Integer Dim row As Integer, col As Integer table = frmMain.BookServer.getAccountDetails(AccountName) rows = UBound(table, 1) - LBound(table, 1) + 1 cols = UBound(table, 2) - LBound(table, ...