AutoCompleting QLineEdit

AutoCompleter.py

from PyQt4.QtCore import QEvent, Qt
from PyQt4.QtGui import QLineEdit

class MyLineEdit(QLineEdit):
    def __init__(self, *args, **kwargs):
        QLineEdit.__init__(self, *args, **kwargs)
        
        self.completions = [] # All available completions
        self.partials = [] # Parsed completions according to partially typed word
        
        self.cursorpos = 0
        self.wordstart = -1 # Start of word where cursor positioned
        self.wordend = -1 # End of word where cursor is positioned
        self.lastindex = -1 # Last used completion of available completions
        
    def addCompletion(self, word):
        if not word in self.completions:
            self.completions.append(word)
            
    def delCompletion(self, word):
        if word in self.completions:
            self.completions.remove(word)
            
    def setCompletions(self, items):
        self.completions = items
        
    def getWords(self):
        text = str(self.text())
        
        if self.lastindex == -1:
            self.cursorpos = self.cursorPosition()
            self.wordstart = text.rfind(" ", 0, self.cursorpos) + 1
        
        pattern = text[self.wordstart:self.cursorpos]
        
        self.partials = [item for item in self.completions if item.lower().startswith(pattern.lower())]
        return self.partials
        
    def applyCompletion(self, text):
        old = str(self.text())
        self.wordend = old.find(" ", self.cursorpos)
        
        if self.wordend == -1:
            self.wordend = len(old)
            
        new = old[:self.wordstart] + text + old[self.wordend:]
        self.setText(new)
        
    def event(self, event):
        if event.type() == QEvent.KeyPress:
            if event.key() == Qt.Key_Tab:
                if not len(self.completions):
                    return True
                
                if self.lastindex >= len(self.getWords()) or self.lastindex == -1:
                    self.lastindex = 0
                    
                # only one item in the completion list
                if len(self.partials) == 1:
                    self.applyCompletion(self.partials[0])

                # more than one remaining matches
                else:
                    match = self.partials[self.lastindex]
                    self.lastindex += 1
                    self.applyCompletion(match)
                return True
            else:
                self.lastindex = -1
                
        return QLineEdit.event(self, event)

def main(): 
    import sys
    from PyQt4.QtGui import QLabel, QVBoxLayout, QApplication, QWidget
    
    LIST_DATA = ['a', 'aardvark', 'aardvarks', 'aardwolf',
             'abacus', 'babel', 'bach', 'cache', 
             'daggle', 'facet', 'kabob', 'kansas']
             
    app = QApplication(sys.argv) 
    
    # objects
    w = QWidget() 
    label = QLabel(w)
    text = "Possible completions: \n" + \
        "%s\n" + \
        "Press Tab to autocomplete, multiple times " + \
        "to cycle thru available completions"
    label.setText(text % ", ".join(LIST_DATA))
    lineedit = MyLineEdit(w)
    lineedit.setCompletions(LIST_DATA)

    # layout
    layout = QVBoxLayout()
    layout.addWidget(label)
    layout.addWidget(lineedit)
    w.setLayout(layout)
    
    # go
    w.show() 
    sys.exit(app.exec_()) 
    
if __name__ == "__main__": 
    main()