*args question

[grocery_stocker]

Given the following code...

#!/usr/bin/env python

import time
import thread

def myfunction(string,sleeptime,*args):
while 1:

print string
time.sleep(sleeptime) #sleep for a specified amount of time.

if __name__=="__main__":

thread.start_new_thread(myfunction,("Thread No:1",2))

while 1ass

Taken from following URL....
http://linuxgazette.net/107/pai.html


How can myfunction() extract the tuple ("Thread No:1",2) from
start_new_thread() if myfunction is only being passed the single arg
("Thread No:1",2)

 

[grocery_stocker]

Given the following code...

#!/usr/bin/env python

import time
import thread

def myfunction(string,sleeptime,*args):
while 1:

print string
time.sleep(sleeptime) #sleep for a specified amount of time.

if __name__=="__main__":

thread.start_new_thread(myfunction,("Thread No:1",2))

while 1ass

Taken from following URL....http://linuxgazette.net/107/pai.html

How can myfunction() extract the tuple ("Thread No:1",2) from
start_new_thread() if myfunction is only being passed the single arg
("Thread No:1",2)

The only thing that I think of is that the tuple ("Thread No:1",2) is
somehow being extract before it gets passed to myfunction(). Ie,
something like the following...

[cdalten@localhost ~]$ python
Python 2.4.3 (#1, Oct 1 2006, 18:00:19)
[GCC 4.1.1 20060928 (Red Hat 4.1.1-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information..... print "The formal args are: ", args
.... print "the first value is:", first
.... print "the second value is:", second
....The formal args are: ()
the first value is: 1
the second value is: 2

 

[John Machin]

Given the following code...

#!/usr/bin/env python

import time
import thread

def myfunction(string,sleeptime,*args):
    while 1:

        print string
        time.sleep(sleeptime) #sleep for a specified amount of time.

if __name__=="__main__":

    thread.start_new_thread(myfunction,("Thread No:1",2))

    while 1ass

Taken from following URL....http://linuxgazette.net/107/pai.html

How can myfunction() extract the tuple ("Thread No:1",2) from
start_new_thread() if myfunction is only being passed the single arg
("Thread No:1",2)

The only thing that I think of is that the tuple ("Thread No:1",2) is
somehow being extract before it gets passed to myfunction(). Ie,
something like the following...

[cdalten@localhost ~]$ python
Python 2.4.3 (#1, Oct  1 2006, 18:00:19)
[GCC 4.1.1 20060928 (Red Hat 4.1.1-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information.>>> def myfunction(first, second, *args):

...     print "The formal args are: ", args
...     print "the first value is:", first
...     print "the second value is:", second
...>>> a, b = (1,2)
The formal args are:  ()
the first value is: 1
the second value is: 2

Manual sez:
thread.start_new_thread(function, args[, kwargs])
where args must be a tuple

so thread.start_new_thread does this (ignoring the kwargs):
function(*args)
or it would if it were written in Python instead of C.

HTH
John

 

[Tim Chase]

Given the following code...

#!/usr/bin/env python

import time
import thread

def myfunction(string,sleeptime,*args):
while 1:

print string
time.sleep(sleeptime) #sleep for a specified amount of time.

if __name__=="__main__":

thread.start_new_thread(myfunction,("Thread No:1",2))

while 1ass

Taken from following URL....http://linuxgazette.net/107/pai.html

How can myfunction() extract the tuple ("Thread No:1",2) from
start_new_thread() if myfunction is only being passed the single arg
("Thread No:1",2)

The only thing that I think of is that the tuple ("Thread No:1",2) is
somehow being extract before it gets passed to myfunction(). Ie,
something like the following...

[cdalten@localhost ~]$ python
Python 2.4.3 (#1, Oct 1 2006, 18:00:19)
[GCC 4.1.1 20060928 (Red Hat 4.1.1-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information.... print "The formal args are: ", args
... print "the first value is:", first
... print "the second value is:", second
...The formal args are: ()
the first value is: 1
the second value is: 2

and if you call "myfunction(1,2,("Thread No:1",2))", you should
get something like

The formal args are: (('Thread No:1', 2),)
the first value is: 1
the second value is: 2

It's a list of the various items you put in:

def show_args(first, second, *args):
print "first", first
print "second", second
for i, arg in enumerate(args):
print "#%i %s" % (i, arg)

So you can either access "args[0]" (which is a bit dangerous, as
you assume there may be a value when there's not), or you can do
the more traditional thing of just treating it like a list as
above (e.g. iterating over it or using it in a list-comprehension).

-tkc

 

[grocery_stocker]

The only thing that I think of is that the tuple ("Thread No:1",2) is
somehow being extract before it gets passed to myfunction(). Ie,
something like the following...

[cdalten@localhost ~]$ python
Python 2.4.3 (#1, Oct 1 2006, 18:00:19)
[GCC 4.1.1 20060928 (Red Hat 4.1.1-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information.

def myfunction(first, second, *args):

... print "The formal args are: ", args
... print "the first value is:", first
... print "the second value is:", second
...

a, b = (1,2)
myfunction(a,b)

The formal args are: ()
the first value is: 1
the second value is: 2

and if you call "myfunction(1,2,("Thread No:1",2))", you should
get something like

The formal args are: (('Thread No:1', 2),)
the first value is: 1
the second value is: 2

It's a list of the various items you put in:

def show_args(first, second, *args):
print "first", first
print "second", second
for i, arg in enumerate(args):
print "#%i %s" % (i, arg)

So you can either access "args[0]" (which is a bit dangerous, as
you assume there may be a value when there's not), or you can do
the more traditional thing of just treating it like a list as
above (e.g. iterating over it or using it in a list-comprehension).

Maybe I'm missing it, but in the original code, the line had

thread.start_new_thread(myfunction,("Thread No:1",2))

It has a single arg ("Thread No:1",2) versus something like

thread.start_new_thread(myfunction,1, 2, ("Thread No:1",2))

But

def myfunction(string,sleeptime,*args):

clearly takes two args. I don't get how the single arg ("Thread No:1",
2) in start_new_thread() gets magically converted two arges, string
and sleeptime, before it reaches myfunction().

 

[Tim Chase]

Maybe I'm missing it, but in the original code, the line had

thread.start_new_thread(myfunction,("Thread No:1",2))

It has a single arg ("Thread No:1",2) versus something like

thread.start_new_thread(myfunction,1, 2, ("Thread No:1",2))

But

def myfunction(string,sleeptime,*args):

clearly takes two args. I don't get how the single arg ("Thread No:1",
2) in start_new_thread() gets magically converted two arges, string
and sleeptime, before it reaches myfunction().

As John pointed out, the start_new_thread passes *args to your
function. So you would define a your function:

def myfunc(some_string, some_int):
print "The string value:", some_string
print "The int value", some_int

thread.start_new_thread(myfunc, "some string", 42)

should print

The string value: some string
The int value: 42

because all the subsequent values after the function-handle/name
get passed into the function when it gets called. As if the
start_new_thread() function was defined as

def start_new_thread(fn, *args, **kwargs):
thread_magic_happens_here()
result = fn(*args, **kwargs)
return more_thread_magic_happens_here(result)

-tkc

 

[Tim Chase]

thread.start_new_thread(myfunc, "some string", 42)

This should have been

thread.start_new_thread(myfunc, ("some string", 42))

because all the subsequent values after the function-handle/name
get passed into the function when it gets called. As if the
start_new_thread() function was defined as

def start_new_thread(fn, *args, **kwargs):
thread_magic_happens_here()
result = fn(*args, **kwargs)
return more_thread_magic_happens_here(result)

and this should have been

def start_new_thread(fn, args=[], kwargs={}):
thread_magic()
result = fn(*args, **kwargs)

My threading-library usage is a little rusty, so I forgot those
were literal parameters, not args/kwargs that became more
idiomatic in other code authored later.

-tkc

 

[Dave Angel]

Try the following, to call your function yourself in this way:


def myfunction(string,sleeptime,*args):
while 1:

print "string is ", string
time.sleep(sleeptime) #sleep for a specified amount of time.

f = myfunction
r = ("Thread No:1",2)
f(*r)

The key here is the *r syntax, which is used in a function call to
turn a tuple (or list) into a separate set of arguments. It's kind of
the inverse of the *args you're already using.

DaveA

 

[Aahz]

Given the following code...

import thread

Here's your problem; subclass threading.Thread instead, much easier.
--
Aahz ([email protected]) <*> http://www.pythoncraft.com/

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are, by
definition, not smart enough to debug it." --Brian W. Kernighan