Modelview programming in PyQt4

Question

In my first attempt, I have tried to load images from disk and load it to a QTableView using QAbstractTableModel. I'd like a general code review of this code.

import sys
import os

from PyQt4 import QtGui, QtCore

class MyListModel(QtCore.QAbstractTableModel): 
    def __init__(self, datain, col, thumbRes, parent=None): 
        """ datain: a list where each item is a row
        """
        self._thumbRes = thumbRes
        QtCore.QAbstractListModel.__init__(self, parent) 
        self._listdata = datain
        self._col = col
        self.pixmap_cache = {}

    def colData(self, section, orientation, role):
        if role == QtCore.Qt.DisplayRole:
            return None

    def headerData(self, section, orientation, role):
        if role == QtCore.Qt.DisplayRole:
            if orientation in [QtCore.Qt.Vertical, QtCore.Qt.Horizontal]:
                return None

    def rowCount(self, parent=QtCore.QModelIndex()): 
        return len(self._listdata) 

    def columnCount(self, parent):
        return self._col

    def data(self, index, role):
        if role == QtCore.Qt.SizeHintRole:
            return  QtCore.QSize(*self._thumbRes)

        if role == QtCore.Qt.TextAlignmentRole:
            return QtCore.Qt.AlignCenter

        if role == QtCore.Qt.EditRole:
            row = index.row()
            column = index.column()
            try:
                fileName = os.path.split(self._listdata[row][column])[-1]
            except IndexError:
                return
            return fileName

        if role == QtCore.Qt.ToolTipRole:
            row = index.row()
            column = index.column()
            try:
                self.selectonChanged(row,column)
                fileName = os.path.split(self._listdata[row][column])[-1]
            except IndexError:
                return
            return QtCore.QString(fileName)

        if index.isValid() and role == QtCore.Qt.DecorationRole:
            row = index.row()
            column = index.column()
            try:
                value = self._listdata[row][column]
            except IndexError:
                return

            pixmap = None
            # value is image path as key
            if self.pixmap_cache.has_key(value) == False:
                pixmap=self.generatePixmap(value)
                self.pixmap_cache[value] =  pixmap
            else:
                pixmap = self.pixmap_cache[value]
            return QtGui.QImage(pixmap).scaled(self._thumbRes[0],self._thumbRes[1], 
                QtCore.Qt.KeepAspectRatio)

        if index.isValid() and role == QtCore.Qt.DisplayRole:
            row = index.row()
            column = index.column()
            try:
                value = self._listdata[row][column]
                fileName = os.path.split(value)[-1]
            except IndexError:
                return
            return os.path.splitext(fileName)[0]

    def generatePixmap(self, value):
        pixmap=QtGui.QPixmap()
        pixmap.load(value)
        return pixmap

    def flags(self, index):
        return QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable

    def setData(self, index, value, role=QtCore.Qt.EditRole):
        if role == QtCore.Qt.EditRole:
            row = index.row()
            column = index.column()
            try:
                newName = os.path.join(str(os.path.split(self._listdata[row][column])[0]), str(value.toString()))
            except IndexError:
                return
            self.__renameFile(self._listdata[row][column], newName)
            self._listdata[row][column] = newName
            self.dataChanged.emit(index, index)
            return True
        return False

    def selectonChanged(self, row, column):
        # TODO Image scale
        pass


    def __renameFile(self, fileToRename, newName):
        try:
            os.rename(str(fileToRename), newName)
        except Exception, err:
            print err


class MyTableView(QtGui.QTableView):
    """docstring for MyTableView"""
    def __init__(self):
        super(MyTableView, self).__init__()
        self.setWindowFlags(QtCore.Qt.Widget | QtCore.Qt.FramelessWindowHint | QtCore.Qt.X11BypassWindowManagerHint)
        sw = QtGui.QDesktopWidget().screenGeometry(self).width()
        sh = QtGui.QDesktopWidget().screenGeometry(self).height()
        self.setGeometry(0,0,sw,sh)
        self.showFullScreen()

        thumbWidth = 300
        thumbheight = 420
        col = sw/thumbWidth 
        self.setColumnWidth(thumbWidth, thumbheight)
        crntDir = "/Users/UserName/Pictures/"
        # create table
        list_data = []
        philes = os.listdir(crntDir)
        for phile in philes:
            if phile.endswith(".png") or phile.endswith("jpg"):
                list_data.append(os.path.join(crntDir, phile))
        _twoDLst = convertToTwoDList(list_data, col)

        lm = MyListModel(_twoDLst, col, (thumbWidth, thumbheight), self)
        self.setShowGrid(False)

        self.setWordWrap(True)
        self.setModel(lm)
        self.resizeColumnsToContents()
        self.resizeRowsToContents()

    def keyPressEvent(self, keyevent):
        """ Capture key to exit, next image, previous image,
            on Escape , Key Right and key left respectively.
        """
        event = keyevent.key()
        if event == QtCore.Qt.Key_Escape:
            self.close()

def convertToTwoDList(l, n): 
    return [l[i:i+n] for i in range(0, len(l), n)]

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    window =  MyTableView()
    window.show()
    window.raise_()
    sys.exit(app.exec_())

Answer 1

Abstract Model

There are a few improvements I could see in your table model class:

1. In data() you could use elif for all of the if-statements past the first. This will save the need to evaluate each if-condition after the first condition that was found to be True

2. Use key in dict notation. You have this line in your data() method:

   if self.pixmap_cache.has_key(value) == False:
   

   This can be written simpler and more Pythonic-ly as:

   if not value in self.pixmap_cache:
   

3. In setData() you caste the result from os.path.split() to a str. This is not necessary as os.path.split() returns a tuple containing strings.

4. Finally, in your selectionChanged() function, raise a NotImplementedError instead of passing. Just in case.

Table

1. In your __init__() function, you set the current directory. You have hard-coded some basic user information. Instead, use the function os.path.expanduser. This will expand ~ into the current user's information.

   crntDir = os.path.expanduser('~/Pictures/')
   

2. In your for-loop checking for file extensions, you simply check for phile.endswith('jpg'). This will match anything that ends with jpg, including directories. Add the period and it will be fixed.

3. There is no need to store MyListModel in a variable. Just go ahead and declare it in self.setModel().

General Comments

1. In your convertToTwoDList function, make your variable names more descriptive. They are very ambiguous at the moment.
2. Look over the PEP8 style guide. It will help your code look more Pythonic. A few examples:
   use_underscores in variable names instead of camelCase. Keep consistent spacing throughout your code. Overall it looks very good, however there are times where you have double-blank lines in-between methods.