I'm using the validatecommand option of a Tkinter Entry box to pickup the value entered by the user and validate it in a database. This works successfully once per Entry widget.

Problem is, the event won't fire again a second time for the same widget, say if a user returns to make a correction. How can I reset validation on an Entry widget so it can be executed again if the user returns to the box later?

def isOkay(root, why, where, barcode, name):
    
    if (barcode != ''): 
        lookupFromBarcodeSql = "select Manufacturer, Brand, Model, Submodel, Size from Drives where Submodel = %s and Manufacturer = 'Seagate' and Brand != '' and Brand is not null and Model != '' and Model is not null and Submodel != '';"
        lookupFromBarcodeParams = (barcode.strip(),)

        myCursor.execute(lookupFromBarcodeSql, lookupFromBarcodeParams)
        lookupResults = myCursor.fetchall()
        for result in lookupResults:
            print(result[0]   " "   result[1]   " "   result[2]   " "   result[4])
    
checkAgainstDb, = root.register(isOkay)

lidBarCode = Entry(BarCodeFrame, validate="focusout",validatecommand=(checkAgainstDb, '%d','%i','%S','%P','%W'))


The callback function is unfinished code but is only called once, as evidenced by the print statement only firing once. 

CodePudding user response：

There are paths through isOkay that do not return True or False. Validation functions must return a boolean value or it will get disabled.