Custom delegate with completions from file

rock_type.py

from PyQt5.QtCore import QFile, QIODevice, Qt
from PyQt5.QtWidgets import QStyledItemDelegate, QComboBox

# noinspection PyUnresolvedReferences
from orexplore.gui.ui import rock_types_rc  # noqa


class RockTypeDelegate(QStyledItemDelegate):

    def __init__(self, parent=None):
        super(RockTypeDelegate, self).__init__(parent)

        self._availableTypes = []

        # Read available rock types from resource file.
        name = ':/rock_types/all.txt'
        file = QFile(name)

        if not file.open(QIODevice.ReadOnly):
            raise IOError('{}: {}'.format(name, file.errorString()))

        while not file.atEnd():
            type = unicode(file.readLine().trimmed(), 'utf-8')
            self._availableTypes.append(type)

    def setEditorData(self, editor, index):
        editor.setCurrentText(index.data(Qt.EditRole))
        editor.lineEdit().selectAll()

    def createEditor(self, parent, option, index):
        comboBox = QComboBox(parent)
        comboBox.setEditable(True)

        for type in self._availableTypes:
            comboBox.addItem(type)

        return comboBox