Why widgets become 'NoneType'?

[woooee]

The error is with the labels not the canvas.  All labels will have an
id of "None" as that is what pack() returns.
         lbl = Label(win, text=astr[i]).pack(side=LEFT )
         labels.append(lbl)
The error will come up in the config_labels function when the program
tries to config a tuple of "None", if not before.  Other than that,
the previous suggestion, post the entire error message so we know
where an what is happening, is required to debug further.