Réponse acceptée !
désolé, j'avais oublié de le mentionner!

mais ce n'est plus la peine, j'ai trouvé comment faire avec Tkinter:
def popupChoices(self, event=None):
"""Popup right-click menu of special parameter operations"""
selectedFileList = self.listbox.curselection()
if selectedFileList != ():
self.frame = Frame(self.window, relief=RIDGE)
self.entry = Entry(self.frame, width = '21')
self.menu = Menu(self.entry, tearoff = 0)
self.menu.add_command(label = "Keep Rep Version",command =
self.cmdsGetRepVersion)
self.menu.add_command(label = "Keep WE Version",command =
self.cmdsKeepWorkingVersion)
self.menu.add_command(label = "Keep Merge Files",command =
self.cmdsKeepMergedVersion)
self.menu.add_command(label = "Manual Merge",command =
self.cmdsMergefiles)
self.menu.add_separator()
self.menu.add_command(label = "Add Element",command =
self.cmdsAddElement)
self.menu.add_command(label = "Remove Element",command =
self.cmdsRemoveElement)
self.menu.add_separator()
self.menu.add_command(label = "Edit File",command =
self.cmdsEditFile)
self.menu.add_separator()
self.menu.add_command(label = "Select All",command =
self.cmdsSelectAll)
# Get the current y-coordinate of the Entry
ycoord = self.entry.winfo_pointery()
# Get the current x-coordinate of the cursor
xcoord = self.entry.winfo_pointerx()
#
Display the Menu as a popup as it is not associated with a Button
self.menu.tk_popup(xcoord, ycoord)
puis dans le main:
self.listbox.bind('<Button-3>', self.popupChoices)
voilà!!!