Modifying code to drag strings

Question

I was stuck trying to understand the code that I came across from Bryan Oakley here. Currently, this code allows the user to drag two ovals using tkinter. I wanted to be able to modify this code so that instead of ovals, the user is able to drag strings (key-value pairs) from two lists and match them. For instance, I want the user to be able to drag a string like "User" from one list and "Ryan" from another list and match them. I would greatly appreciate any input on how I should go about to modify the code so the user is able to drag the two strings.

import Tkinter as tk

class SampleApp(tk.Tk):
    '''Illustrate how to drag items on a Tkinter canvas'''

    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)

        # create a canvas
        self.canvas = tk.Canvas(width=400, height=400)
        self.canvas.pack(fill="both", expand=True)

        # this data is used to keep track of an 
        # item being dragged
        self._drag_data = {"x": 0, "y": 0, "item": None}

        # create a couple movable objects
        self._create_token((100, 100), "white")
        self._create_token((200, 100), "black")

        # add bindings for clicking, dragging and releasing over
        # any object with the "token" tag
        self.canvas.tag_bind("token", "<ButtonPress-1>", self.OnTokenButtonPress)
        self.canvas.tag_bind("token", "<ButtonRelease-1>", self.OnTokenButtonRelease)
        self.canvas.tag_bind("token", "<B1-Motion>", self.OnTokenMotion)

    def _create_token(self, coord, color):
        '''Create a token at the given coordinate in the given color'''
        (x,y) = coord
        self.canvas.create_oval(x-25, y-25, x+25, y+25, 
                                outline=color, fill=color, tags="token")

    def OnTokenButtonPress(self, event):
        '''Being drag of an object'''
        # record the item and its location
        self._drag_data["item"] = self.canvas.find_closest(event.x, event.y)[0]
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def OnTokenButtonRelease(self, event):
        '''End drag of an object'''
        # reset the drag information
        self._drag_data["item"] = None
        self._drag_data["x"] = 0
        self._drag_data["y"] = 0

    def OnTokenMotion(self, event):
        '''Handle dragging of an object'''
        # compute how much this object has moved
        delta_x = event.x - self._drag_data["x"]
        delta_y = event.y - self._drag_data["y"]
        # move the object the appropriate amount
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        # record the new position
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

if __name__ == "__main__":
    app = SampleApp()
    app.mainloop()

Answer 1

Is this what you are looking for:

import tkinter as tk

class SampleApp(tk.Tk):
    '''Illustrate how to drag items on a Tkinter canvas'''

    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)

        # create a canvas
        self.canvas = tk.Canvas(width=400, height=400, bg='red')
        self.canvas.pack(fill="both", expand=True)

        # this data is used to keep track of an 
        # item being dragged
        self._drag_data = {"x": 0, "y": 0, "item": None}

        # create a couple movable objects
        self._create_token((100, 100), "white", "User")
        self._create_token((200, 100), "black", "Ryan")

        # add bindings for clicking, dragging and releasing over
        # any object with the "token" tag
        self.canvas.tag_bind("token", "<ButtonPress-1>", self.OnTokenButtonPress)
        self.canvas.tag_bind("token", "<ButtonRelease-1>", self.OnTokenButtonRelease)
        self.canvas.tag_bind("token", "<B1-Motion>", self.OnTokenMotion)

    def _create_token(self, coord, color, mytext):
        '''Create a token at the given coordinate in the given color'''
        (x,y) = coord
        self.canvas.create_text(x-25, y-25,  
                                fill=color, tags="token", text=mytext)

    def OnTokenButtonPress(self, event):
        '''Being drag of an object'''
        # record the item and its location
        self._drag_data["item"] = self.canvas.find_closest(event.x, event.y)[0]
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def OnTokenButtonRelease(self, event):
        '''End drag of an object'''
        # reset the drag information
        self._drag_data["item"] = None
        self._drag_data["x"] = 0
        self._drag_data["y"] = 0

    def OnTokenMotion(self, event):
        '''Handle dragging of an object'''
        # compute how much this object has moved
        delta_x = event.x - self._drag_data["x"]
        delta_y = event.y - self._drag_data["y"]
        # move the object the appropriate amount
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        # record the new position
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

if __name__ == "__main__":
    app = SampleApp()
    app.mainloop()

?

What I changed:
(EDITED LINES: 10, 18, 19, 27, 30 and 31)
-canvas background color from default (white) to red to identify white and black objects on it better;
-self.canvas.create_oval to self.canvas.create_text since you want strings instead of ovals;
-also, removed the second couple of coordinates (x+25, y+25) since create_text requires only one couple of coordinates (create_oval requires two of them), and removed outline=color since a text object doesn't have outline option, so Tkinter returns an unknown option error;
-and finally, after changing it from create_oval to create_text, I had to add the text option mytext to the _create_token function (def _create_token(self, coord, color, mytext):) and its instances ("User" & "Ryan") to the movable objects:
self._create_token((100, 100), "white", "User") self._create_token((200, 100), "black", "Ryan").