Derek Martin a écrit :
I'd like to know if it's possible to code something in Python which
would be equivalent to the following C:
[Assume bool is typedef'd to int, and TRUE and FALSE are #defined to 1
and 0, respectively]
---- debug.c ----
#include <stdio.h>
bool DEBUG;
void dprint(char *msg)
{
if (DEBUG){
printf("DEBUG: %s", msg);
}
}
This should have been:
fprintf(STDERR, "DEBUG: %s", msg);
STDOUT is for *normal* program outputs. Debug informations, warnings,
and all verbosity should go to STDERR.
---- end of debug.c ----
The idea being that all modules of the program would "import" this
code via the header file:
---- debug.h ----
extern bool DEBUG;
void dprint(char *msg);
---- end of debug.h ----
I'm specifically trying to avoid having to create a debug object and
pass it around... All modules should have visibility into the state of
whether DEBUG is turned on or off, and be able to use dprint(). Can
Python do this?
Yes, indeed.
I tried creating debug.py as such:
---- debug.py ----
DEBUG = True
def dprint(msg):
if DEBUG:
print("DEBUG: %s" % msg)
---- end ----
Same remark : please use sys.stderr
Then in the modules that wanted to use it, I did:
from debug import DEBUG, dprint
But I got some weird behavior. The imported copy
It's not a copy.
of DEBUG is
read-only;
It's not read-only.
if you update it, the name DEBUG points to a different
object which the other modules can't see.
Indeed : the way you imported it explicitely made it a (module) local name.
After doing some reading of
the docs, this behavior is explained and understood (though obviously
not what I want). It just occured to me that I might be able to get
around that by using a setter function in the module itself...
Just use a fully qualified name, so you dont make DEBUG local:
import debug
print debug.DEBUG
debug.DEBUG = True
print debug.DEBUG
Now note that ALL_UPPER names are - by convention - considered
'constants'. If this is supposed to be altered, don't write it ALL_UPPER.
The other weird behavior was, once I changed the value of DEBUG,
dprint() started to behave oddly. No matter what I passed as an
argument (and no matter what I set the value of DEBUG to be), it
started printing the exact literal string:
DEBUG: %s
>
whenever it was called. It was as if the function couldn't see the
parameter msg, which was passed via the call. Most unexpected, and
definitely undesirable.
I just fail to see how the code you posted could expose such a
behaviour. Please post actual code.
Also and FWIW, Python has a logging module in it's stdlib. Please use it
instead of any half-backed squared-wheel homegrown solution.
My 2 cents
--
http://mail.python.org/mailman/listinfo/python-list
