Comments on: Downloading Large Files Async With GIO

By: Download Files Async With Gio And Python | jonobacon@home

Download Files Async With Gio And Python | jonobacon@home — Mon, 15 Mar 2010 19:37:43 +0000

[...] I asked for some help on how to download a file without blocking the GUI. Thanks to everyone who contributed their expertise in the post comments: I now have my program [...]

By: chris

chris — Mon, 15 Mar 2010 13:54:42 +0000

If you just want to download the file you probably should use copy_async().

By: Benjamin Otte

Benjamin Otte — Mon, 15 Mar 2010 13:48:43 +0000

Why don’t you just copy the file using http://library.gnome.org/devel/gio/stable/GFile.html#g-file-copy-async – or its pygtk equivalent?

By: Stuart Ward

Stuart Ward — Mon, 15 Mar 2010 13:09:01 +0000

Wouldn't it be easier to use subprocess module to execute a wget commend. command = ['wget',path_name] wget_process = subprocess.Popen(command)

You can then check on when it is complete with the wget_process.returncode == None if it is still running.

By: Johan Dahlin

Johan Dahlin — Mon, 15 Mar 2010 11:37:07 +0000

A mostly async example is available here:

http://git.gnome.org/browse/pygobject/tree/examples/gio/downloader.py

By: punch bag stand | punching bag sets

punch bag stand | punching bag sets — Mon, 15 Mar 2010 10:45:34 +0000

[...] Downloading Large Files Async With GIO | jonobacon@home [...]

By: Joaquim Rocha

Joaquim Rocha — Mon, 15 Mar 2010 10:15:40 +0000

Hi Jono,

I have a simple Python app for the N900 and I make a few async calls in it.

The concept is really simple, I have an Async worker which is a thread and has a queue of items to be dealt with. An item receives a target method to execute and a callback to be called when it is done, each with its respective arguments.

Then the items are put in the queue and the async worker just goes through running them.

Here you have the code for the AsyncWorker and Items:

http://gitorious.org/seriesfinale/seriesfinale/blobs/master/src/SeriesFinale/asyncworker.py

Take a look here for an example of how it’s used:

http://gitorious.org/seriesfinale/seriesfinale/blobs/master/src/SeriesFinale/series.py

Hope it helps you,

By: Alexander Larsson

Alexander Larsson — Mon, 15 Mar 2010 08:45:40 +0000

If you want the whole file contents then you should use load_contents_async/load_contents_finish as Jan said. read_async() just returns an opened stream you can read from.

However, all this is void unless you also enable threads by calling g_thread_init() (or whatever this is in python) early in your app. Its not possible to implement async local file i/o without threads, so when its not enabled gio "emulates" it by reading from idle handlers.

Additionally, this part of your code: outputfile = open("/home/jono/Desktop/shot.ogg","w") outputfile.writelines(f)

Is not async and will block your app.

By: Tomeu Vizoso

Tomeu Vizoso — Mon, 15 Mar 2010 08:44:13 +0000

Already considered connecting both streams with gio.OutputStream.splice_async()?

By: herodiade

herodiade — Mon, 15 Mar 2010 08:36:35 +0000

Hi, I’m not an expert but I think at least the write isn’t async here (this alone can freeze, esp. on slow disks). And I think (not sure) the read callback will be triggered as soon as the fd opened by read_async() is available (if so read_finish(result).read() will block).

There’s a complete and working example (using gio’s copy_async()) in Rhythmbox source code : http://osdir.com/ml/general/2010-02/msg24291.html http://git.gnome.org/browse/rhythmbox/tree/plugins/magnatune/magnatune/MagnatuneSource.py

The faq.pygtk example isn’t likely to block because it doesn’t write() as your code snippet do, and only display 100 bytes (less than a single tcp packet, should be fully available in one shot when the read callback is triggered or soon after).