<code Python>

from __future__ import print_function

import sys

try :
   from PyQt5.QtCore import *
   from PyQt5.QtGui import *
   from PyQt5.QtWidgets import *
   print ("using PyQt5")
except :
   from PyQt4.QtCore import *
   from PyQt4.QtGui import *
   print ("using PyQt4")

# pip3 install PyQt5
# Debian, Ubuntu: apt-get install python3-pyqt5
# Fedora: dnf install python3-qt5
# ArchLinux: pacman -S python-pyqt5 

class Window (QMainWindow) :

    def __init__ (self, parent = None) :
       super (Window, self).__init__ (parent)
       
       self.tree = QTreeWidget ()
       self.tree.itemDoubleClicked.connect (self.itemClick)
       
       self.tab = QTabWidget ()
       
       splitter = QSplitter (self)
       splitter.addWidget (self.tree)
       splitter.addWidget (self.tab)
       self.setCentralWidget (splitter)
               
       self.displayDir (self.tree, ".")
       
    def itemClick (self, item, column) :
        if sys.version_info >= (3, 0) :
           path = item.data (0, Qt.UserRole)
        else :
           path = item.data (0, Qt.UserRole).toString()
        info = QFileInfo (path)
        ext = "." + info.completeSuffix ()
        widget = None
        if ext in [ ".h", ".cpp" ] :
           widget = QTextEdit ()
           f = QFile (path)
           if f.open (QFile.ReadOnly) :
              data = f.readAll ()
              if sys.version_info >= (3, 0) :
                 data = str (data, "latin1")
              else:
                 data = str (data)
                  
              widget.setText (data)
        if widget == None :
            widget =  QWidget ()
        self.tab.addTab (widget, info.fileName ())

    def displayDir (self, target, path) :
        localDir = QDir (path) 
        dir = QDir (localDir.absolutePath ())
        item = QTreeWidgetItem (target)
        item.setText (0, dir.dirName ())
        item.setToolTip (0, dir.absolutePath ())
        item.setData (0, Qt.UserRole, dir.absolutePath ())
        item.setForeground (0, QColor ("red"))
        
        infoList = dir.entryInfoList (QDir.Files | QDir.Dirs |
                                      QDir.NoDotAndDotDot)
        for info in infoList :
          if info.isDir () :
             self.displayDir (item, info.filePath ()) 
          else :
             node = QTreeWidgetItem (item)
             node.setText (0, info.fileName ())
             node.setToolTip (0, info.filePath ())
             node.setData (0, Qt.UserRole, info.filePath ())
             node.setForeground (0, QColor ("blue"))

app = QApplication (sys.argv)
win = Window ()
win.show ()
app.exec_ ()


</code>

<code Python>
from __future__ import print_function

import sys

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

app = QApplication (sys.argv)
win = QPushButton ()
win.setText ("knoflik")
win.show ()
app.exec_ ()
</code>

<code C++>

from __future__ import print_function

import sys

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

class Window (QPushButton) :

    def __init__ (self, parent = None) :
       super (Window, self).__init__ (parent)
       self.setText ("knoflik")
       self.clicked.connect (self.click)

    def click (self):
       self.setText ("click")

app = QApplication (sys.argv)
win = Window ()
win.show ()
app.exec_ ()
</code>


pip3 install PyQt5

Debian, Ubuntu: apt-get install python3-pyqt5

Fedora: dnf install python3-qt5

ArchLinux: pacman -S python-pyqt5