Adding a right click context menu with link with multiple widgets?

Making as few changes as possible to the current code, you need to do three things:

1. Create a global variable to hold a reference to the currently selected label.

2. Inside popup, set this variable to event.widget, which will be the currently selected label.

3. Inside print_label, print this label's text by accessing its "text" key.

Below is a fixed version of your program. The stuff I changed is in the comment box:

from Tkinter import * # Tkinter -> tkinter in Python 3

root = Tk()

#############################################################
selected = None  # This is the variable mentioned in step 1

def print_label():
    print selected["text"]  # This is step 3

def popup(event):
    global selected  # Tell Python that selected is global

    menu.post(event.x_root, event.y_root)

    selected = event.widget  # This is step 2
#############################################################

# create a popup menu
menu = Menu(root, tearoff=0)
menu.add_command(label="Display the label", command=print_label)


# create the 3 labels
label1_text=StringVar()
label2_text=StringVar()
label3_text=StringVar()

label1_text.set("my label 1")
label2_text.set("my label 2")
label3_text.set("my label 3")

label1=Label(root, textvariable=label1_text)
label2=Label(root, textvariable=label2_text)
label3=Label(root, textvariable=label3_text)

label1.pack()
label2.pack()
label3.pack()

# attach popup to frame
label1.bind("<Button-3>", popup)
label2.bind("<Button-3>", popup)
label3.bind("<Button-3>", popup)

root.mainloop()