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threading+ftp+import => block

P: n/a
Hi,
I'm experiencing a strange problem while trying to manage a ftp connection
into a separate thread.

I'm on linux, python 2.4.3

Here is a test :
------ ftp_thread.py ------
import ftplib
import threading
import datetime

class test( threading.Thread ) :
ftp_conn = ftplib.FTP("localhost","user","pass")
def run( self ) :
print self.ftp_conn.pwd()
self.ftp_conn.dir("/")
print datetime.date.today()
def t() :
t = test()
t.start()
t.join()
t()
-------

If I do :
$ python ftp_thread.py
/
drwxrwsr-x 2 panard ftp 4096 Jul 24 12:48 archives
2006-07-24
==Works perfectly

But :
$ python
>>import ftp_thread
/
<program block>

For a strange reason, I've tried to add theses lines before the 't()' call :

ftp_conn = ftplib.FTP("localhost","user","pass")
ftp_conn.dir("/")

And then, when calling t(), self.ftp_conn.dir("/") shows the list ! (I guess
a problem of globals()/import .. ?)
But... the program now blocks just before displaying today date...

I guess I'm doing something really wrong with threads.. but I don't know
what...

Any hints?

Thanks

Panard
Jul 24 '06 #1
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2 Replies


P: n/a
Panard wrote:
Hi,
I'm experiencing a strange problem while trying to manage a ftp connection
into a separate thread.

I'm on linux, python 2.4.3

Here is a test :
------ ftp_thread.py ------
import ftplib
import threading
import datetime

class test( threading.Thread ) :
ftp_conn = ftplib.FTP("localhost","user","pass")
def run( self ) :
print self.ftp_conn.pwd()
self.ftp_conn.dir("/")
print datetime.date.today()
def t() :
t = test()
t.start()
t.join()
t()
-------

If I do :
$ python ftp_thread.py
/
drwxrwsr-x 2 panard ftp 4096 Jul 24 12:48 archives
2006-07-24
==Works perfectly

But :
$ python
>>>import ftp_thread
/
<program block>
This has been documented in the blog posts titled "How well you know Python"
(find it on google)

The problem is that, once you run "import ftp_thread" a lock is set in the
Python interpreter, so then you can't start a new thread... (this from the
back of my mind).

--
damjan
Jul 26 '06 #2

P: n/a
Damjan wrote:
Panard wrote:
>Hi,
I'm experiencing a strange problem while trying to manage a ftp
connection into a separate thread.

I'm on linux, python 2.4.3

Here is a test :
------ ftp_thread.py ------
import ftplib
import threading
import datetime

class test( threading.Thread ) :
ftp_conn = ftplib.FTP("localhost","user","pass")
def run( self ) :
print self.ftp_conn.pwd()
self.ftp_conn.dir("/")
print datetime.date.today()
def t() :
t = test()
t.start()
t.join()
t()
-------

If I do :
$ python ftp_thread.py
/
drwxrwsr-x 2 panard ftp 4096 Jul 24 12:48 archives
2006-07-24
==Works perfectly

But :
$ python
>>>>import ftp_thread
/
<program block>

This has been documented in the blog posts titled "How well you know
Python" (find it on google)

The problem is that, once you run "import ftp_thread" a lock is set in the
Python interpreter, so then you can't start a new thread... (this from the
back of my mind).
Actually, testing with
class test( threading.Thread ) :
def run( self ) :
print 'Hello'

instead of your test class, didn't show this anomally... actually the
problem is that "import ftp_thread" sets a lock on *importing* other
modules and I thing that the call to "self.ftp_conn.dir("/")" deep down in
the ftplib module tries to "import re" and that's where it hangs.

You could try to move the "import re" in ftplib to the top of the module,
and submit a patch to the Python bug system.

Here's a simpler test class that hangs:

import threading
class test(threading.Thread):
import string
print 'Step one'
def run(self):
import re
print 'Hangs before this when this file is imported'

def t() :
t = test()
t.start()
t.join()
t()

--
damjan
Jul 26 '06 #3

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