Folyamatjelző - Egyszerű alkalmazás vázlata szálak (threads) használatára



A szálak (threads) alkalmazására kézen fekvő példa az, amikor egy ftp serverről letöltünk egy állományt és a felhasználónak - hogy lássa mi történik - egy folyamatjelzővel (progressbar) kijelezzük, hogy hol tart folyamat. A következő kód a megvalósítás alapötletét mutatja be.

Folyamatjelzőként Michael Lange progressbar widget-jét fogom használni annyi módosítással, hogy a Tkinter.Frame osztály helyett a Tkinter.Toplevel osztályból származtatom le: 


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#! /usr/bin/env python
'''Michael Lange 
The Meter class provides a simple progress bar widget for Tkinter.

INITIALIZATION OPTIONS:
The widget accepts all options of a Tkinter.Frame plus the following:

    fillcolor -- the color that is used to indicate the progress of the
                 corresponding process; default is "orchid1".
    value -- a float value between 0.0 and 1.0 (corresponding to 0% - 100%)
             that represents the current status of the process; values higher
             than 1.0 (lower than 0.0) are automagically set to 1.0 (0.0); default is 0.0 .
    text -- the text that is displayed inside the widget; if set to None the widget
            displays its value as percentage; if you don't want any text, use text="";
            default is None.
    font -- the font to use for the widget's text; the default is system specific.
    textcolor -- the color to use for the widget's text; default is "black".

WIDGET METHODS:
All methods of a Tkinter.Frame can be used; additionally there are two widget specific methods:
    
    get() -- returns a tuple of the form (value, text)
    set(value, text) -- updates the widget's value and the displayed text;
                        if value is omitted it defaults to 0.0 , text defaults to None .
'''

import Tkinter

class Meter(Tkinter.Frame):
    def __init__(self, master, width=300, height=20, bg='white', fillcolor='orchid1',\
                 value=0.0, text=None, font=None, textcolor='black', *args, **kw):
        Tkinter.Frame.__init__(self, master, bg=bg, width=width, height=height, *args, **kw)
        self._value = value

        self._canv = Tkinter.Canvas(self, bg=self['bg'], width=self['width'], height=self['height'],\
                                    highlightthickness=0, relief='flat', bd=0)
        self._canv.pack(fill='both', expand=1)
        self._rect = self._canv.create_rectangle(0, 0, 0, self._canv.winfo_reqheight(), fill=fillcolor,\
                                                 width=0)
        self._text = self._canv.create_text(self._canv.winfo_reqwidth()/2, self._canv.winfo_reqheight()/2,\
                                            text='', fill=textcolor)
        if font:
            self._canv.itemconfigure(self._text, font=font)

        self.set(value, text)
        self.bind('', self._update_coords)

    def _update_coords(self, event):
        '''Updates the position of the text and rectangle inside the canvas when the size of
        the widget gets changed.'''
        # looks like we have to call update_idletasks() twice to make sure
        # to get the results we expect
        self._canv.update_idletasks()
        self._canv.coords(self._text, self._canv.winfo_width()/2, self._canv.winfo_height()/2)
        self._canv.coords(self._rect, 0, 0, self._canv.winfo_width()*self._value, self._canv.winfo_height())
        self._canv.update_idletasks()

    def get(self):
        return self._value, self._canv.itemcget(self._text, 'text')

    def set(self, value=0.0, text=None):
        #make the value failsafe:
        if value < 0.0:
            value = 0.0
        elif value > 1.0:
            value = 1.0
        self._value = value
        if text == None:
            #if no text is specified use the default percentage string:
            text = str(int(round(100 * value))) + ' %'
        self._canv.coords(self._rect, 0, 0, self._canv.winfo_width()*value, self._canv.winfo_height())
        self._canv.itemconfigure(self._text, text=text)
        self._canv.update_idletasks()

##-------------demo code--------------------------------------------##

def _demo(meter, value):
    meter.set(value)
    if value < 1.0:
        value = value + 0.005
        meter.after(50, lambda: _demo(meter, value))
    else:
        meter.set(value, 'Demo successfully finished')

if __name__ == '__main__':
    root = Tkinter.Tk(className='meter demo')
    m = Meter(root, relief='ridge', bd=3)
    m.pack(fill='x')
    m.set(0.0, 'Starting demo...')
    m.after(1000, lambda: _demo(m, 0.0))
    root.mainloop()

A feladat megoldása a következő lépésekből áll:

Nem készítek GUI-t, hogy a kód a lehető legrövidebb legyen. Ezért a server nevét, a felhasználónevet, a jelszót, a forráskönyvtár elérési útját, a letöltendő file nevét, a célkönyvtárat a Globals osztály attribútumaiban fogom tárolni (11-21. sorok).


A fileletöltés szála akkor szűnik meg, amikor teljesen letöltődött a file.
A folyamatjelző programszálában arról kell gondoskodni, hogy a value nevű változó a letöltött filerésznek megfelelő értéket vegyen fel és ezzel az értékkel hívjuk meg a folyamatjelző objektumunk set() metódusát amikor a szál megkapja a processzoridőt. Ezért a letöltött filerész méretét a ThreadProgressBar osztály run() metódusában (110-134. sorok) egy ciklusban fogjuk beolvasni a célkönyvtárból. (A ThreadProgressBar osztály run() metódusához a progressbar widget _demo() függvénye adja az ötletet.) A ciklusból akkor lépünk ki, amikor letöltöttük a file-t. Ez egyben a szál befejezését is jelenti.
A script főszálának végrehajtását a fileletöltés és a folyamatjelző szálak join() metódusának hívásával addig blokkoljuk, amíg a két szál meg nem szűnik. 


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#!/usr/bin/env python
# -*- coding: Utf-8 -*-

import sys
import os
import Tkinter
import ftplib
import threading

#--------------------------------------------------------------------------------------------
class Globals:
    #local parameters
    racine = '/home/peter/Documents/ftp_progressindicator/'     #destination path on the local pc
    fullPathName = ""						
    totalFileSize = 0
    #server parameters
    server = "mirrors.sth.sze.hu"
    user = "anonymous"
    password = "none"
    directory = "/linux/suse/i386/9.3"				#source directory on the ftp server
    fileName = "ChangeLog"					#file to download
#--------------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------------
'''Michael Lange 
The Meter class provides a simple progress bar widget for Tkinter.
http://tkinter.unpythonic.net/wiki/ProgressMeter

INITIALIZATION OPTIONS:
The widget accepts all options of a Tkinter.Frame plus the following:

    fillcolor -- the color that is used to indicate the progress of the
                 corresponding process; default is "orchid1".
    value -- a float value between 0.0 and 1.0 (corresponding to 0% - 100%)
             that represents the current status of the process; values higher
             than 1.0 (lower than 0.0) are automagically set to 1.0 (0.0); default is 0.0 .
    text -- the text that is displayed inside the widget; if set to None the widget
            displays its value as percentage; if you don't want any text, use text="";
            default is None.
    font -- the font to use for the widget's text; the default is system specific.
    textcolor -- the color to use for the widget's text; default is "black".

WIDGET METHODS:
All methods of a Tkinter.Frame can be used; additionally there are two widget specific methods:
    
    get() -- returns a tuple of the form (value, text)
    set(value, text) -- updates the widget's value and the displayed text;
                        if value is omitted it defaults to 0.0 , text defaults to None .
'''

class Meter(Tkinter.Toplevel):
    def __init__(self, master, width=300, height=20, bg='white', fillcolor='orchid1',\
                 value=0.0, text=None, font=None, textcolor='black', *args, **kw):
        Tkinter.Toplevel.__init__(self, bg=bg, width=width, height=height, *args, **kw)

        
        self._value = value

        self._canv = Tkinter.Canvas(self, bg=self['bg'], width=self['width'], height=self['height'],\
                                    highlightthickness=0, relief='flat', bd=0)
        self._canv.pack(fill='both', expand=1)
        self._rect = self._canv.create_rectangle(0, 0, 0, self._canv.winfo_reqheight(), fill=fillcolor,\
                                                 width=0)
        self._text = self._canv.create_text(self._canv.winfo_reqwidth()/2, self._canv.winfo_reqheight()/2,\
                                            text='', fill=textcolor)
        if font:
            self._canv.itemconfigure(self._text, font=font)

        self.set(value, text)
        self.bind('<Configure>', self._update_coords)

    def _update_coords(self, event):
        '''Updates the position of the text and rectangle inside the canvas when the size of
        the widget gets changed.'''
        # looks like we have to call update_idletasks() twice to make sure
        # to get the results we expect
        self._canv.update_idletasks()
        self._canv.coords(self._text, self._canv.winfo_width()/2, self._canv.winfo_height()/2)
        self._canv.coords(self._rect, 0, 0, self._canv.winfo_width()*self._value, self._canv.winfo_height())
        self._canv.update_idletasks()

    def get(self):
        return self._value, self._canv.itemcget(self._text, 'text')

    def set(self, value=0.0, text=None):
        #make the value failsafe:
        if value < 0.0:
            value = 0.0
        elif value > 1.0:
            value = 1.0
        self._value = value
        if text == None:
            #if no text is specified use the default percentage string:
            text = str(int(round(100 * value))) + ' %'
        self._canv.coords(self._rect, 0, 0, self._canv.winfo_width()*value, self._canv.winfo_height())
        self._canv.itemconfigure(self._text, text=text)
        self._canv.update_idletasks()
#--------------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------------
class ThreadProgressBar(threading.Thread):
       #def __init__(self, parent, prBar):
       """Animacios parameterek inicializalasa"""
       def __init__(self, prBar):
           threading.Thread.__init__(self)
           self.prBar_ = prBar
           self.value = 0.0
           self.prBar_.set('Starting demo...')	 

       def run(self):
           while 1:
               try:
                  self.fileSize = os.path.getsize(Globals.fullPathName)
               except OSError, err:
                  pass       		 #meg nem letezik a file
               else:
                  break

           while self.fileSize != Globals.totalFileSize:
               try:
                  self.fileSize = os.path.getsize(Globals.fullPathName)
               except OSError, err:
                  self.fileSize = 0.0    #meg nem letezik a file

               if self.fileSize != Globals.totalFileSize :  
                  if self.fileSize == 0.0:
                     self.value =0.0
                  else:
                     self.value = (0.0 + self.fileSize)/Globals.totalFileSize

                  self.prBar_.set(self.value)    
           else:
               self.prBar_.set(1, 'Demo successfully finished')
               self.prBar_.master.destroy()
#--------------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------------
class FileDownload:
    def __init__(self):
        "Incorporate file download functionality."
        
    def connectToServer(self):
        try:
             self.ftp = ftplib.FTP(Globals.server)                      #connect to host, default port
             self.ftp.login(Globals.user, Globals.password)             #user 'anonymous', passwd 'none'
             self.ftp.cwd(Globals.directory)                            #Change directory    
             Globals.totalFileSize = self.ftp.size(Globals.fileName)    #read filesize and store it in a global
        except ftplib.all_errors, err:
            print err
     
    def fileContent(self, fname_):
        #Downloads file
        try:
            f=open(Globals.racine+fname_,"w")	
            self.ftp.retrbinary("RETR " + fname_, f.write)
        except ftplib.all_errors, e:
            print "Error :", e
        
    def deconnectFromServer(self):
        self.ftp.quit()
#--------------------------------------------------------------------------------------------

#--------------------------------------------------------------------------------------------
class ThreadFileDownload(threading.Thread):
    def __init__(self, downL):
        threading.Thread.__init__(self)
        self.downL = downL	

    def run(self):
        self.downL.fileContent(Globals.fileName)
#--------------------------------------------------------------------------------------------


######################################################################
if __name__ == '__main__':
    title = 'Thread demo'
    root = Tkinter.Tk()
    root.title(title)
    root.withdraw()
    Globals.fullPathName = Globals.racine + Globals.fileName
    fileDownload = FileDownload()
    fileDownload.connectToServer()
    tfileDownload = ThreadFileDownload(fileDownload)
    m = Meter(root, relief='ridge', bd=3)
    tProgressBar = ThreadProgressBar(m)
    tfileDownload.start()
    tProgressBar.start()
    tfileDownload.join()
    tProgressBar.join()
    fileDownload.deconnectFromServer()
    root.mainloop()