title: Tkinter's grid() geometry manager ignoring ipadx argument
body: <p>While extending the code based on <a href="https://stackoverflow.com/questions/18985260/python-guiinput-and-output-matrices/18986884#18986884">this awesome</a> Bryan Oakley's answer (btw his code works great, it's just me the one that can't make the padding work) I've found that the argument ipadx passed to .grid() is being ignored on the line:</p>
  
  <pre><code>e.grid(row=row, column=column, sticky=tk.N+tk.E+tk.S+tk.W, ipadx=5, ipady=3)
  </code></pre>
  
  <p>from the following script:</p>
  
  <pre><code>import tkinter as tk
  from tkinter import ttk
  
  class SimpleTableInput(tk.Frame):
      def __init__(self, parent, rows, columns):
          tk.Frame.__init__(self, parent)
  
          self._entry = {}
          self.rows = rows
          self.columns = columns
  
          # create the table of widgets
          for row in range(self.rows):
              for column in range(self.columns):
                  index = (row, column)
                  e = ttk.Entry(self, justify='right')
                  e.grid(row=row, column=column, sticky=tk.N+tk.E+tk.S+tk.W, ipadx=5, ipady=3)
                  #e.grid(row=row, column=column, sticky="nsew", ipadx=5, ipady=3)
                  self._entry[index] = e
          # adjust column weights so they all expand equally
          for column in range(self.columns):
              self.grid_columnconfigure(column, weight=1)
          # designate a final, empty row to fill up any extra space
          self.grid_rowconfigure(rows, weight=1)
  
      def get(self):
          '''Return a list of lists, containing the data in the table'''
          result = []
          for row in range(self.rows):
              current_row = []
              for column in range(self.columns):
                  index = (row, column)
                  #current_row.append(self._entry[index].get())
                  current_row.append(self._entry[index].get())
              result.append(current_row)
          return result
  
  class Example(tk.Frame):
      def __init__(self, parent):
          tk.Frame.__init__(self, parent)
          self.table = SimpleTableInput(self, 3, 4)
          self.submit = ttk.Button(self, text="Submit", command=self.on_submit)
          self.table.pack(side="top", fill="both", expand=True)
          self.submit.pack(side="bottom")
  
      def on_submit(self):
          print(self.table.get())
  
  
  root = tk.Tk()
  Example(root).pack(side="top", fill="both", expand=True)
  root.mainloop()
  </code></pre>
  
  <p>So I end up getting no internal padding on the entry widgets, they align the text to the right but leave no space before the ttk.Entry border as can be seen on this image: <a href="https://i.stack.imgur.com/5hQnL.png" rel="nofollow noreferrer">ttk.Entry widgets with no internal x padding</a></p>
  
  <p>One thing that amazes me is that ipady works ok. </p>
  
  <p>Things I've tried:</p>
  
  <ul>
  <li>tk.Entry instead of ttk.Entry</li>
  <li>different values for ipadx (makes no difference at all)</li>
  <li>read the docs to find if another argument could be interfering with ipadx, found nothing (however I regard this as the most probable cause)</li>
  </ul>
  
  <p>If it's of any help, I'm using Tkinter version 8.6 and Python 3.6.2 on windows 7 </p>