title: Center align a group of widgets in a frame
body: <p>If there's a single widget in a frame's row, I can align it to any side with <code>sticky=</code>, or center align by omitting <code>sticky</code>.</p>
  
  <p>However, when there are multiple columns in a row, objects in them end up left-aligned:</p>
  
  <p><a href="https://i.stack.imgur.com/AfdKf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AfdKf.png" alt="left-aligned"></a></p>
  
  <p>while I wish for them to stay in the center (while maintaining size).</p>
  
  <p>Code excerpt:</p>
  
  <pre><code>from Tkinter import N,W,S,E,Tk
  import ttk
  import Tkinter as tkinter
  
  root = Tk()
  mainframe = ttk.Frame(root)
  mainframe.grid(column=0, row=0, sticky=(N, W, E, S))
  mainframe.columnconfigure(0, weight=1)
  mainframe.rowconfigure(0, weight=1)
  
  tv_town_fr = ttk.Frame(mainframe)
  tv_town_fr.grid(row=3, sticky=(W,E))
  
  tv_town_add = ttk.Button(tv_town_fr,text="+",width=4)
  tv_town_add.grid(row=1,column=1)
  tv_town_edit = ttk.Button(tv_town_fr,text="*",width=4)
  tv_town_edit.grid(row=1,column=2)
  tv_town_del = ttk.Button(tv_town_fr,text="-",width=4)
  tv_town_del.grid(row=1,column=3)
  tv_town_up = ttk.Button(tv_town_fr,text=u"↑",width=4)
  tv_town_up.grid(row=1,column=4)
  tv_town_down = ttk.Button(tv_town_fr,text=u"↓",width=4)
  tv_town_down.grid(row=1,column=5)
  
  tv_query_fr = ttk.Frame(mainframe)
  tv_query_fr.grid(row=6, sticky=(W,E))
  
  tv_query_add = ttk.Button(tv_query_fr,text="+",width=5)
  tv_query_add.grid(row=1,column=1)
  tv_query_edit = ttk.Button(tv_query_fr,text="*",width=5)
  tv_query_edit.grid(row=1,column=2)
  tv_query_del = ttk.Button(tv_query_fr,text="-",width=5)
  tv_query_del.grid(row=1,column=3)
  tv_query_up = ttk.Button(tv_query_fr,text=u"↑",width=5)
  tv_query_up.grid(row=1,column=4)
  tv_query_down = ttk.Button(tv_query_fr,text=u"↓",width=5)
  tv_query_down.grid(row=1,column=5)
  </code></pre>