Enter key press

from gi.repository import Gtk as gtk, Gdk as gdk
import os

class mainClass():
        def __init__(self):
                cssStyle = gtk.CssProvider()
                cssOpen = open(("css.css"),"rb")
                cssRead = cssOpen.read()
                cssOpen.close()
                cssStyle.load_from_data(cssRead)

                gtk.StyleContext.add_provider_for_screen(
                        gdk.Screen.get_default(),
                        cssStyle,
                        gtk.STYLE_PROVIDER_PRIORITY_APPLICATION
                        )

                windowMain = gtk.Window()
                windowMain.set_size_request(500,300)
                windowMain.connect("destroy", lambda w: gtk.main_quit())

                grid = gtk.Grid()
                windowMain.add(grid)

                #middle#
                scrolledwindowOutputs = gtk.ScrolledWindow()
                scrolledwindowOutputs.set_hexpand(True)
                scrolledwindowOutputs.set_vexpand(True)
                grid.attach(scrolledwindowOutputs,0,1,3,1)

                self.textviewOutputs = gtk.TextView()
                self.textbufferOutputs = self.textviewOutputs.get_buffer()
                scrolledwindowOutputs.add(self.textviewOutputs)

                #bottom#
                self.entryCommand = gtk.Entry()
                self.entryCommand.set_hexpand(True)
                self.entryCommand.connect("key-release-event",self.commandOutputs)
                grid.attach(self.entryCommand,0,2,1,1)
                windowMain.show_all()
                gtk.main()

        def commandOutputs(self,widget,keyEvent,data=None):
                if keyEvent.keyval == gdk.KEY_Escape:
                        entryRead = self.entryCommand.get_text()
                        processRun = os.popen(entryRead)
                        self.processRead = processRun.read()
                        processRun.close()
                        print(self.processRead)

mainClass()