Re: Python equivalent for C module

[Gary Herron]

Derek Martin wrote:

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);
}
}

---- 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?

I tried creating debug.py as such:

---- debug.py ----
DEBUG = True
def dprint(msg):
if DEBUG:
print("DEBUG: %s" % msg)
---- end ----

Then in the modules that wanted to use it, I did:

from debug import DEBUG, dprint

So don't import it that way. Instead, do it this way:

import debug

Then us like this:
debug.DEBUG = True
and
debug.dprint(.. .)

Lots of other possibilities exist -- but this solves your specific first
question.

But I got some weird behavior. The imported copy of DEBUG is
read-only; if you update it, the name DEBUG points to a different
object which the other modules can't see. 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... I'll
try this later.

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 don't believe it -- send your *actual* code, and we'll all have a look.

Gary Herron

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