Noob can't make threads work

[Steve Horsley]

I am trying to start two threads to do some time consuming work. This is my
first stab at threading, and it isn't working as I expect. Instead of the
threads starting when I call start(), they seem to run the target code as
part of the constructor call.

Here is my test code...

#!/usr/bin/python

import time
import threading

def fiddle():
for n in range(3):
print n
time.sleep(1)

print 'Creating threads...'
t1 = threading.Thread(target=fiddle())
t2 = threading.Thread(target=fiddle())
print 'Starting threads...'
t1.start()
t2.start()


I was expecting output like this:

Creating threads...
Starting threads...
0
0
1
1
2
2

but I get this instead:

Creating threads...
0
1
2
0
1
2
Starting threads...

This is in python 2.3 on Linux and also python 2.4 on XP.
Either threading in Python is badly broken, or I'm missing something
fundamental. I know which is most likely, but I can't figure it out.

Could someone point me in the right direction, plese?

TIA
Steve

 

[Grant Edwards]

I am trying to start two threads to do some time consuming work. This is my
first stab at threading, and it isn't working as I expect. Instead of the
threads starting when I call start(), they seem to run the target code as
part of the constructor call.

Here is my test code...

#!/usr/bin/python

import time
import threading

def fiddle():
for n in range(3):
print n
time.sleep(1)

print 'Creating threads...'
t1 = threading.Thread(target=fiddle())
t2 = threading.Thread(target=fiddle())

t1 = threading.Thread(target=fiddle)
t2 = threading.Thread(target=fiddle)

 

[Steve Horsley]

t1 = threading.Thread(target=fiddle)
t2 = threading.Thread(target=fiddle)

Doh! Slap that forehead!

Of course, I was calling fiddle() and using the
return value (None) as the target argument. And
a Thread with a target of None does nothing
when start()ed.

Many thanks.
Steve

 

[Grant Edwards]

Doh! Slap that forehead!

Of course, I was calling fiddle() and using the
return value (None) as the target argument. And
a Thread with a target of None does nothing
when start()ed.

Been there, done that.

 

[Steve Holden]

Been there, done that.

And, speaking of T-shirts, time for this week's reminder that PyCon is
now only three weeks away!

regards
Steve