title: How to modify the default font in Tkinter?
body: <p>I'm working on a GUI in Python2.7, with Tkinter, and I have an annoying problem.</p>
  <p>I would like to define the default font used by all the widgets, if possible in one line.
  This line modify only the font used in Entry, or ComboBox:</p>
  <pre><code>root.option_add(&quot;*Font&quot;, &quot;courier 10&quot;)
  </code></pre>
  <p>but not the label of checkbox by example.</p>
  <p>I found that a predefined font exist &quot;TkDefaultFont&quot; but I'm unable to change its configuration:</p>
  <pre><code>print tkFont.Font(font='TkDefaultFont').configure()
  tkFont.Font(font='TkDefaultFont').config(family='Helvetica', size=20)
  tk.TkDefaultFont = tkFont.Font(family=&quot;Helvetica&quot;,size=36,weight=&quot;bold&quot;)
  print tkFont.Font(font='TkDefaultFont').configure()
  </code></pre>
  <p>prints:</p>
  <p><code>{'family': 'DejaVu Sans', 'weight': 'normal', 'slant': 'roman', 'overstrike': 0, 'underline': 0, 'size': -12}</code><br/>
  <code>{'family': 'DejaVu Sans', 'weight': 'normal', 'slant': 'roman', 'overstrike': 0, 'underline': 0, 'size': -12}</code></p>
  <p>(no errors, but nothing changed!)</p>
  <p>What I'm doing wrong?</p>