[Tutor] Tk canvas question

Kent Johnson kent37 at tds.net
Tue Aug 23 13:18:56 CEST 2005

Ìúʯ wrote:
>    I am writing a resource manager like program !
> the files of directory is display on canvas and taged.
> the tag and file name is keep in a dictionary!
> The tag is a increaseing number from 1,so I build the 
> dictionary like (1:file1,2:file2,......).
> While geting into another directory,I try to remove all 
> object and tags on the canvas so that the tags would be 
> count form 1 again.But I found out the tag number is 
> increasing, not recount form 1. My dictionary can be 
> organize that simple.

This sounds like a bug in your program; you should be able to start over with the tags. Can you show us some code?

>    I want to know is there a way to get the tag of canvas 
> recount form 1 again? or even more simple ,get the filename 
> I had wrote in canvas directly? 

You can use the itemcget() method of the canvas to retrieve the text:

 >>> root = Tk()
 >>> canvas=Canvas(root)
 >>> t=canvas.create_text(10, 10, text='Hello', tag='1')
 >>> canvas.pack()
 >>> canvas.itemcget('1', 'text')

There does seem to be something strange with reusing the tags - if I create a new element with tag '1' I can't retrieve it by tag:

 >>> canvas.delete('1')
 >>> t=canvas.create_text(10, 10, text='Goodbye', tag='1')
 >>> canvas.itemcget('1', 'text')
 >>> canvas.find_withtag('1')

even though if I ask what tags are on the item it says '1':

 >>> t
 >>> canvas.itemcget(2, 'text')
 >>> canvas.itemcget(2, 'tags')
 >>> canvas.find_withtag('1')

Maybe you could just remember the handles to the text items instead of using tags?


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