How to write verbose scripts

[Steven D'Aprano]

I find myself writing command line tools in Python where I wish to
include "verbose" output to stdout.

I start with a helper function:
def print_(obj, level=0):
if _verbosity >= level:
print obj
And then I end up with functions or methods looking like this:
def parrot(x)
print_("precond ition", level=2)
do_something()
print_("status is good...", level=1)
print_("parrot is squawking strongly now", level=2)
do_something_el se()
print_("squawk squawk squawk", level=3)
do_more()
print_("postcon dition", level=1)
return something
That often means that my functions end up with more message printing code
than actual code. The whole thing seems messy and hard to manage for all
but the smallest scripts.

Worst of all, sometimes the messages I wish to print may be expensive to
compute, and I don't want to waste time computing them if they aren't
going to be printed because the verbosity is too low. But nor do I wish
to fill my code with this:

if _verbosity >= 3:
x = calculate_compl icated_thing()
print_(x, level=3)

Is there a better way of doing this than the way I am going about it?

--
Steven

[Ben Finney]

Steven D'Aprano <st***@REMOVE-THIS-cybersource.com .auwrites:

On Tue, 02 Sep 2008 13:07:33 -0400, Joe Riopel wrote:

On Tue, Sep 2, 2008 at 12:55 PM, Steven D'Aprano
<st***@remove-this-cybersource.com .auwrote:

Is there a better way of doing this than the way I am going about it?

Would the logging module help, and just print the output to the stdout
(or a file) instead?

Thank you to everyone who answered.

As I feared, it seems that there's no really simple way of dealing with
arbitrary messages at arbitrary parts of my code.

I would think the 'logging' module *is* the simple way to do this. At
least, it's as simple as it could be without leading to massive
re-visiting of the "arbitrary parts of one's code" when later desiring
to change the way the messages are handled.

--
\ “We must become the change we want to see.� —Mahatma Gandhi |
`\ |
_o__) |
Ben Finney

[Lie]

On Sep 3, 6:31*pm, Uwe Schmitt <rocksportroc.. [e-mail] mwrote:

On 2 Sep., 18:55, Steven D'Aprano <st...@REMOVE-THIS-

cybersource.com .auwrote:

I find myself writing command line tools in Python where I wish to
include "verbose" output to stdout.

I start with a helper function:

def print_(obj, level=0):
* * if _verbosity >= level:
* * * * print obj

And then I end up with functions or methods looking like this:

def parrot(x)
* * print_("precond ition", level=2)
* * do_something()
* * print_("status is good...", level=1)
* * print_("parrot is squawking strongly now", level=2)
* * do_something_el se()
* * print_("squawk squawk squawk", level=3)
* * do_more()
* * print_("postcon dition", level=1)
* * return something

That often means that my functions end up with more message printing code
than actual code. The whole thing seems messy and hard to manage for all
but the smallest scripts.

Worst of all, sometimes the messages I wish to print may be expensive to
compute, and I don't want to waste time computing them if they aren't
going to be printed because the verbosity is too low. But nor do I wish
to fill my code with this:

if _verbosity >= 3:
* * x = calculate_compl icated_thing()
* * print_(x, level=3)

Is there a better way of doing this than the way I am going about it?

--
Steven

You can save some code if you use function decorators for logging
input and output values of
functions.
So write lots of functions containing one statement and your problem
is solved ;-)

Greetings, Uwe

That would be perfect if python is a fully functional language (read
that as: purely functional language). Functional language dictates no
side effects, so logging input and output of functions is pretty much
everything needed to do debugging (which is the main reason for having
verbose mode). It would still be feasible, though, if you keep
yourself from using functions with side-effects (or use as few of them
as possible).

Bjorn Lindqvist says:

One big downside with that approach is that it becomes much harder to
grep for the log message. Usually when I go through logs, I don't care
what exactly the message says, just that it is easily googleable (uses
some kind of identifying text) and that it is unique so I can know
exactly where it was emitted.

Actually, I'd prefer a log code (perhaps also as an option, to use -e
for showing up log code besides the log message). The log code would
be unique and referenced only once in the whole application (to nail
down who said what to a single point). The code would make a call to
the log printer with the log code (not the error string) and a few
arguments to be interpolated to the error string (taken from a
dictionary indexed by error code).

The downside is loss of inline documentation by the logging codes.