Image viewer desktop app in python

qt-viewer.py

import os
import glob
import sys
import subprocess
from PySide2.QtWidgets import*
from PySide2.QtGui import*
from PySide2 import QtCore, QtGui


# initialise variables
index = 0
file = ""
application = QApplication(sys.argv)


# keys
def left_press():
    global index
    print("LEFT!")
    index -= 1
    load_pic()


def right_press():
    global index, files
    print("RIGHT!")
    if index < (len(files)-1):
        index += 1
    load_pic()


# function to quit
def quit_app():
    global application
    print("Quit!")
    application.exit()


# select in file manager
def select_file():
    global file

    if sys.platform == 'darwin':
        subprocess.run(['open', '-R', file])
    elif sys.platform == 'linux':
        subprocess.Popen(['nautilus', file])
    else:
        command = 'C:\\windows\\explorer /select,"{}"'.format(file)
        print(command)
        subprocess.run([command])

    print("{}: {}".format(sys.platform, file))


# rotate 90
def rotate_picture():
    global window, file, files, index, label
    file = files[index]
    picture = label.pixmap()
    transform = QTransform().rotate(90)
    picture = picture.transformed(transform)
    label.setPixmap(picture)
    label.setGeometry(QtCore.QRect(10, 40, picture.width(), picture.height()))
    window.resize(picture.width()+20, picture.height()+100)
    window.setWindowTitle(file)
    window.show()


# Create a Window
window = QWidget()
window.setWindowTitle("View Image")
window.grabKeyboard()
label = QLabel(window)

# buttons
button = QPushButton("Quit", window)
button.clicked.connect(quit_app)
button.setShortcut(QtGui.QKeySequence.Cancel)

left = QPushButton("< Prev", window)
left.clicked.connect(left_press)
left.setShortcut(QtGui.QKeySequence.MoveToPreviousChar)
left.move(110, 0)

right = QPushButton("Next >", window)
right.clicked.connect(right_press)
right.setShortcut(QtGui.QKeySequence.MoveToNextChar)
right.move(195, 0)

select = QPushButton("Select", window)
select.clicked.connect(select_file)
select.setShortcut(QtGui.QKeySequence.MoveToNextLine)
select.move(295, 0)

rotate = QPushButton("Rotate", window)
rotate.clicked.connect(rotate_picture)
rotate.setShortcut(QtGui.QKeySequence.MoveToPreviousLine)
rotate.move(380, 0)


# get the list of images
pic_dir = "/home/chrisg/Pictures/"
files = glob.glob(pic_dir + "*.jpg")
files += glob.glob(pic_dir + "*.png")
files += glob.glob(pic_dir + "*.gif")
files.sort(key=os.path.getmtime, reverse=True)


# load pictures
def load_pic():
    global window, file, files, index, label
    file = files[index]
    print("{} {} ".format(index, file))
    picture = QPixmap(file)
    label.setPixmap(picture)
    label.setGeometry(QtCore.QRect(10, 40, picture.width(), picture.height()))
    window.resize(picture.width()+20, picture.height()+100)
    window.setWindowTitle(file)
    window.show()


# display the first picture
load_pic()

# wait for events
sys.exit(application.exec_())