Python Tkinter module not showing output

Add this to your code root.mainloop(), Here's a tutorial.

In response to your comment

#Also note that `from <module> import *` is generally frowned upon
#since it can lead to namespace collisions. It's much better to only
#explicitly import the things you need.
from Tkinter import Tk, Label
root = Tk()
w = Label(root, text="Hello, world!")
w.pack()
root.mainloop()

As other answers have pointed out, you need to call mainloop on the root object.

I recommend an OO-style of programming, and I also recommend not doing a global import (ie: not 'from Tkinter import *').

Here's a template I usually start out with:

import Tkinter as tk

class ExampleView(tk.Frame):
    def __init__(self, root):
        tk.Frame.__init__(self, root)
        l = tk.Label(self, text="your widgets go here...", anchor="c")
        l.pack(side="top", fill="both", expand=True)

if __name__=='__main__':
    root = tk.Tk()
    view = ExampleView(root)
    view.pack(side="top", fill="both", expand=True)
    root.mainloop()

This makes it easy to keep your main logic at the start of the file, and keep the creation of the root and the calling of mainloop together, which I think makes the code a little bit easier to understand. It also makes reusing this code a little easier (ie: you could create a larger program where this is one of several windows that can be created)