title: How to clear tkinter combobox?
body: <p>I'm using multiple comboboxes in tkinter, I've passed a list of values to each box. </p>
  
  <p>Currently, after you choose an option you can't clear that box, some selection remains</p>
  
  <p>I want to be able to clear all boxes or have a "blank" value if you want to unselect a box.</p>
  
  <p>So far I've tried assigning a separate button to clear the whole selection but I get errors.
  The button is assigned this command:</p>
  
  <pre><code>for c in categories:
      ttk.Label(text=c, relief=tk.RIDGE, width=15).grid(row=r,column=0)
      categoriesParts = ttk.Combobox(root, textvariable = listVariables[r], values=listMakers[r],width=10, state="readonly")
      categoriesParts.grid(row=r,column=1)
      r = r + 1
  
  def clearComboBox():
      categoriesParts.delete(0, END)
  
  browseButton_Clear = tk.Button(text='Clear Config', command=clearComboBox, bg='green', fg='white')
  </code></pre>
  
  <p>I get errors saying: 
  AttributeError: module 'tkinter.ttk' has no attribute 'tk'</p>
  
  <p>EDIT: working code, if anyone needs:</p>
  
  <pre><code>list_of_widgets = []
  
  for c in categories:
      ttk.Label(text=c, relief=tk.RIDGE, width=15).grid(row=r,column=0)
      categoriesParts = ttk.Combobox(root, textvariable = listVariables[r], values=listMakers[r], width=10, state="readonly")
      categoriesParts.grid(row=r,column=1)
      list_of_widgets.append(categoriesParts)
      r = r + 1
  
  def clearComboBox():
      for widget in list_of_widgets:
          widget.set('')
  
  browseButton_Clear = tk.Button(text='Clear Config', command=clearComboBox, bg='green', fg='white')
  
  
  </code></pre>