python3+PyQt5 implements histogram

#!/usr/bin/env python3

import random
import sys
from PyQt5.QtCore import (QAbstractListModel, QAbstractTableModel,
  QModelIndex, QSize, QTimer, QVariant, Qt,pyqtSignal)
from PyQt5.QtWidgets import (QApplication, QDialog, QHBoxLayout,
  QListView, QSpinBox, QStyledItemDelegate,QStyleOptionViewItem, QWidget)
from PyQt5.QtGui import QColor,QPainter,QPixmap

class BarGraphModel(QAbstractListModel):
 dataChanged=pyqtSignal(QModelIndex,QModelIndex)
 def __init__(self):
  super(BarGraphModel, self).__init__()
  self.__data = []
  self.__colors = {}
  self.minValue = 0
  self.maxValue = 0


 def rowCount(self, index=QModelIndex()):
  return len(self.__data)


 def insertRows(self, row, count):
  extra = row + count
  if extra >= len(self.__data):
   self.beginInsertRows(QModelIndex(), row, row + count - 1)
   self.__data.extend([0] * (extra - len(self.__data) + 1))
   self.endInsertRows()
   return True
  return False


 def flags(self, index):
  #return (QAbstractTableModel.flags(self, index)|Qt.ItemIsEditable)
  return (QAbstractListModel.flags(self, index)|Qt.ItemIsEditable)

 def setData(self, index, value, role=Qt.DisplayRole):
  row = index.row()
  if not index.isValid() or 0 > row >= len(self.__data):
   return False
  changed = False
  if role == Qt.DisplayRole:
   value = value
   self.__data[row] = value
   if self.minValue > value:
    self.minValue = value
   if self.maxValue < value:
    self.maxValue = value
   changed = True
  elif role == Qt.UserRole:
   self.__colors[row] = value
   #self.emit(SIGNAL("dataChanged(QModelIndex,QModelIndex)"),
   #   index, index)
   self.dataChanged[QModelIndex,QModelIndex].emit(index, index)
   changed = True
  if changed:
   #self.emit(SIGNAL("dataChanged(QModelIndex,QModelIndex)"),
    #   index, index)
   self.dataChanged[QModelIndex,QModelIndex].emit(index, index)
  return changed


 def data(self, index, role=Qt.DisplayRole):
  row = index.row()
  if not index.isValid() or 0 > row >= len(self.__data):
   return QVariant()
  if role == Qt.DisplayRole:
   return self.__data[row]
  if role == Qt.UserRole:
   return QVariant(self.__colors.get(row,
     QColor(Qt.red)))
  if role == Qt.DecorationRole:
   color = QColor(self.__colors.get(row,
     QColor(Qt.red)))
   pixmap = QPixmap(20, 20)
   pixmap.fill(color)
   return QVariant(pixmap)
  return QVariant()


class BarGraphDelegate(QStyledItemDelegate):

 def __init__(self, minimum=0, maximum=100, parent=None):
  super(BarGraphDelegate, self).__init__(parent)
  self.minimum = minimum
  self.maximum = maximum


 def paint(self, painter, option, index):
  myoption = QStyleOptionViewItem(option)
  myoption.displayAlignment |= (Qt.AlignRight|Qt.AlignVCenter)
  QStyledItemDelegate.paint(self, painter, myoption, index)


 def createEditor(self, parent, option, index):
  spinbox = QSpinBox(parent)
  spinbox.setRange(self.minimum, self.maximum)
  spinbox.setAlignment(Qt.AlignRight|Qt.AlignVCenter)
  return spinbox


 def setEditorData(self, editor, index):
  value = index.model().data(index, Qt.DisplayRole)
  editor.setValue(value)


 def setModelData(self, editor, model, index):
  editor.interpretText()
  model.setData(index, editor.value())


class BarGraphView(QWidget):

 WIDTH = 20

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


 def setModel(self, model):
  self.model = model
  #self.connect(self.model,
  #  SIGNAL("dataChanged(QModelIndex,QModelIndex)"),
  #  self.update)
  self.model.dataChanged[QModelIndex,QModelIndex].connect(self.update)
  #self.connect(self.model, SIGNAL("modelReset()"), self.update)
  self.model.modelReset.connect(self.update)


 def sizeHint(self):
  return self.minimumSizeHint()


 def minimumSizeHint(self):
  if self.model is None:
   return QSize(BarGraphView.WIDTH * 10, 100)
  return QSize(BarGraphView.WIDTH * self.model.rowCount(), 100)


 def paintEvent(self, event):
  if self.model is None:
   return
  painter = QPainter(self)
  painter.setRenderHint(QPainter.Antialiasing)
  span = self.model.maxValue - self.model.minValue
  painter.setWindow(0, 0, BarGraphView.WIDTH * self.model.rowCount(),
       span)
  for row in range(self.model.rowCount()):
   x = row * BarGraphView.WIDTH
   index = self.model.index(row)
   color = QColor(self.model.data(index, Qt.UserRole))
   y = self.model.data(index)
   painter.fillRect(x, span - y, BarGraphView.WIDTH, y, color)


class MainForm(QDialog):

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

  self.model = BarGraphModel()
  self.barGraphView = BarGraphView()
  self.barGraphView.setModel(self.model)
  self.listView = QListView()
  self.listView.setModel(self.model)
  self.listView.setItemDelegate(BarGraphDelegate(0, 1000, self))
  self.listView.setMaximumWidth(100)
  self.listView.setEditTriggers(QListView.DoubleClicked|
          QListView.EditKeyPressed)
  layout = QHBoxLayout()
  layout.addWidget(self.listView)
  layout.addWidget(self.barGraphView, 1)
  self.setLayout(layout)

  self.setWindowTitle("Bar Grapher")
  QTimer.singleShot(0, self.initialLoad)


 def initialLoad(self):
  # Generate fake data
  count = 20
  self.model.insertRows(0, count - 1)
  for row in range(count):
   value = random.randint(1, 150)
   color = QColor(random.randint(0, 255), random.randint(0, 255),
       random.randint(0, 255))
   index = self.model.index(row)
   self.model.setData(index, value)
   self.model.setData(index, QVariant(color), Qt.UserRole)


app = QApplication(sys.argv)
form = MainForm()
form.resize(600, 400)
form.show()
app.exec_()