wxPython - ComboBox & Choice Class


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A wx.ComboBox object presents a list of items to select from. It can be configured to be a dropdown list or with permanent display.

The selected item from the list is displayed in a text field, which by default is editable, but can be set to be read-only in the presence of wx.CB_READONLY style parameter.

wxPython API contains a wx.Choice class, whose object is also a dropdown list, which is permanently read-only.

The parameters used by wx.ComboBox class constructor are −

Wx.ComboBox(parent, id, value, pos, size, choices[], style)

The value parameter is the text to be displayed in the text box of combobox. It is populated from the items in choices[] collection.

The following style parameters are defined for wx.ComboBox −

S.N. Parameters & Description
1

wx.CB_SIMPLE

Combobox with permanently displayed list

2

wx.CB_DROPDOWN

Combobox with dropdown list

3

wx.CB_READONLY

Chosen item is not editable

4

wx.CB_SORT

List is displayed in alphabetical order

The following table shows commonly used methods of wx.ComboBox class −

S.N. methods & Description
1

GetCurrentSelection ()

Returns the item being selected

2

SetSelection()

Sets the item at the given index as selected

3

GetString()

Returns the string associated with the item at the given index

4

SetString()

Changes the text of item at the given index

5

SetValue()

Sets a string as the text displayed in the edit field of combobox

6

GetValue()

Returns the contents of the text field of combobox

7

FindString()

Searches for the given string in the list

8

GetStringSelection()

Gets the text of the currently selected item

Event binders for events generated by this class are as follows −

S.N. Events & Description
1

wx. COMBOBOX

When item from the list is selected

2

wx. EVT_TEXT

When combobox text changes

3

wx. EVT_COMBOBOX_DROPDOWN

When list drops down

4

wx. EVT_COMBOBOX_CLOSEUP

When list folds up

wx.Choice class constructor prototype is as follows −

wx.Choice(parent, id, pos, size, n, choices[], style)

Parameter ā€˜nā€™ stands for number of strings with which the choice list is to be initialized. Like comboBox, the list is populated with items in choices[] collection.

For Choice class, only one style parameter is defined. It is wx.CB_SORT. Only one event binder processes the event emitted by this class. It is wx.EVT_CHOICE.

Example

This example displays the features of wx.ComboBox and wx.Choice. Both objects are put in a vertical box sizer. The lists are populated with items in languages[] List object.

languages = ['C', 'C++', 'Python', 'Java', 'Perl'] 
self.combo = wx.ComboBox(panel,choices = languages) 
self.choice = wx.Choice(panel,choices = languages)

Event binders EVT_COMBOBOX and EVT_CHOICE process corresponding events on them.

self.combo.Bind(wx.EVT_COMBOBOX, self.OnCombo) 
self.choice.Bind(wx.EVT_CHOICE, self.OnChoice)

The following handler functions display the selected item from the list on the label.

def OnCombo(self, event): 
   self.label.SetLabel("selected "+ self.combo.GetValue() +" from Combobox") 
	
def OnChoice(self,event): 
   self.label.SetLabel("selected "+ self.choice.
      GetString( self.choice.GetSelection() ) +" from Choice")

The complete code listing is as follows −

import wx  
class Mywin(wx.Frame): 
   def __init__(self, parent, title): 
      super(Mywin, self).__init__(parent, title = title,size = (300,200)) 
		
      panel = wx.Panel(self) 
      box = wx.BoxSizer(wx.VERTICAL) 
      self.label = wx.StaticText(panel,label = "Your choice:" ,style = wx.ALIGN_CENTRE) 
      box.Add(self.label, 0 , wx.EXPAND |wx.ALIGN_CENTER_HORIZONTAL |wx.ALL, 20) 
      cblbl = wx.StaticText(panel,label = "Combo box",style = wx.ALIGN_CENTRE) 
		
      box.Add(cblbl,0,wx.EXPAND|wx.ALIGN_CENTER_HORIZONTAL|wx.ALL,5) 
      languages = ['C', 'C++', 'Python', 'Java', 'Perl'] 
      self.combo = wx.ComboBox(panel,choices = languages) 
		
      box.Add(self.combo,1,wx.EXPAND|wx.ALIGN_CENTER_HORIZONTAL|wx.ALL,5) 
      chlbl = wx.StaticText(panel,label = "Choice control",style = wx.ALIGN_CENTRE) 
		
      box.Add(chlbl,0,wx.EXPAND|wx.ALIGN_CENTER_HORIZONTAL|wx.ALL,5) 
      self.choice = wx.Choice(panel,choices = languages) 
      box.Add(self.choice,1,wx.EXPAND|wx.ALIGN_CENTER_HORIZONTAL|wx.ALL,5) 
         
      box.AddStretchSpacer() 
      self.combo.Bind(wx.EVT_COMBOBOX, self.OnCombo) 
      self.choice.Bind(wx.EVT_CHOICE, self.OnChoice)
		
      panel.SetSizer(box) 
      self.Centre() 
      self.Show() 
		  
   def OnCombo(self, event): 
      self.label.SetLabel("You selected"+self.combo.GetValue()+" from Combobox") 
		
   def OnChoice(self,event): 
      self.label.SetLabel("You selected "+ self.choice.GetString
         (self.choice.GetSelection())+" from Choice") 
                             
app = wx.App() 
Mywin(None,  'ComboBox and Choice demo') 
app.MainLoop()

The above code produces the following output −

ComboBox Output
wxpython_major_classes.htm
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