python - Download file with Kivy app without locking event loop -

here's kivy application has button , progress bar. when button pressed, zip file downloaded web , unzipped. progress bar advances mark download's progress.

the problem is, downloading locks kivy event loop, freezing application during download. how can download , unzip file in background?

from __future__ import division import os import requests import zipfile kivy.app import app kivy.lang import builder kivy.uix.boxlayout import boxlayout  zip_url = 'https://www.python.org/ftp/python/3.5.1/python-3.5.1-embed-win32.zip' zip_filename = 'python351.zip'  kv_string = """ <rootwidget>     boxlayout:         orientation: "vertical"         button:             id: download_button             text: "download content"             on_press: self.parent.parent.download_content()         progressbar:             id: download_progress_bar             max: 1             value: 0.1 """  builder.load_string(kv_string)   class rootwidget(boxlayout):     def __init__(self, **kwargs):         super(rootwidget, self).__init__(**kwargs)      def download_content(self):         self.ids["download_button"].disabled = true          total_size_kib = 6023182 / 1024 # debug: hardcoded         print("downloading file: %s" % zip_url)         open(zip_filename, 'wb') handle:             response = requests.get(zip_url, stream=true)              if not response.ok:                 print("something went wrong.")                 return              current_size_kib = 0             block in response.iter_content(1024):                 percent_downloaded = current_size_kib / total_size_kib                 if not current_size_kib % 100:                     print("%.2f%% downloaded far" % (percent_downloaded * 100))                 self.ids['download_progress_bar'].value = percent_downloaded                  handle.write(block)                  current_size_kib += 1          self.unzip_content()      def unzip_content(self):         print("unzipping file")         fh = open(zip_filename, 'rb')         z = zipfile.zipfile(fh)         zip_extract_folder = zip_filename + '_extracted'         if not os.path.exists(zip_extract_folder):             os.makedirs(zip_extract_folder)         z.extractall(zip_extract_folder)         fh.close()         os.remove(zip_filename)          print("done")   class myapp(app):      def build(self):         return rootwidget()   if __name__ == '__main__':     myapp().run() 

first, @nykakin suggests, make download asynchronous, use kivy.network.urlrequest.urlrequest:

def download_content(self):     self.ids["download_button"].disabled = true     req = urlrequest(zip_url, on_progress=self.update_progress,                      chunk_size=1024, on_success=self.unzip_content,                      file_path=zip_filename)  def update_progress(self, request, current_size, total_size):     self.ids['download_progress_bar'].value = current_size / total_size 

second, @keyweeusr suggests, change unzipping method doesn't block event loop, using threading module:

def unzip_content(self, req, result):     threading.thread(target=self.unzip_thread).start()  def unzip_thread(self):     # ... (same unzip_content method in question) 

here's full new version:

from __future__ import division import os import zipfile import threading import time kivy.app import app kivy.lang import builder kivy.uix.boxlayout import boxlayout kivy.network.urlrequest import urlrequest  zip_url = 'https://www.python.org/ftp/python/3.5.1/python-3.5.1-embed-win32.zip' zip_filename = 'python351.zip'  kv_string = """ <rootwidget>     boxlayout:         orientation: "vertical"         button:             id: download_button             text: "download content"             on_press: self.parent.parent.download_content()         progressbar:             id: download_progress_bar             max: 1             value: 0 """  builder.load_string(kv_string)   class rootwidget(boxlayout):      stop = threading.event()          def __init__(self, **kwargs):         super(rootwidget, self).__init__(**kwargs)      def download_content(self):         self.ids["download_button"].disabled = true         req = urlrequest(zip_url, on_progress=self.update_progress,                          chunk_size=1024, on_success=self.unzip_content,                          file_path=zip_filename)      def update_progress(self, request, current_size, total_size):         self.ids['download_progress_bar'].value = current_size / total_size      def unzip_content(self, req, result):         threading.thread(target=self.unzip_thread).start()      def unzip_thread(self):         print("unzipping file")         fh = open(zip_filename, 'rb')         z = zipfile.zipfile(fh)         zip_extract_folder = zip_filename + '_extracted'         if not os.path.exists(zip_extract_folder):             os.makedirs(zip_extract_folder)         z.extractall(zip_extract_folder)         fh.close()         os.remove(zip_filename)         time.sleep(4) # debug: stretch out unzip method test threading          print("done")   class myapp(app):      def on_stop(self):         # kivy event loop stop, set stop signal;         # otherwise app window close, python process         # keep running until secondary threads exit.         self.root.stop.set()              def build(self):         return rootwidget()   if __name__ == '__main__':     myapp().run()