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.