code: def start(self):
  		
  		global parallel
  		for self.i in range(0, self.length):
  			if parallel:
  				self.thread.append(myThread(self.url[ self.i ], self.directory, self.i, 
  								   self.min_file_size, self.max_file_size, self.no_redirects))
  			else:
  				# if not parallel whole url list is passed
  				self.thread.append(myThread(self.url, self.directory, self.i , self.min_file_size, 
  								   self.max_file_size,  self.no_redirects))
  			self.progress[self.i]["value"] = 0
  			self.bytes[self.i] = 0
  			self.thread[self.i].start()
  
  		self.read_bytes()
docs: function to initialize thread for downloading