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

[Joe Riopel]

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?

[Mensanator]

On Sep 2, 11:55 am, 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?

I do something like this, although I don't know if it would
be an improvement.

def collatz(a,p):
""" 3x+1 sequencer, no loop detection

collatz(a,p)
a: starting value
p: print options (binary)
bit 0 print even numbers (turns off power division)
bit 1 print odd numbers
bit 2 print debug (if any)
returns: CollatzSequence Parameters [R1count, R2count]
"""
ONE = gmpy.mpz(1)
TWO = gmpy.mpz(2)
TWE = gmpy.mpz(3)
a = gmpy.mpz(a)
t = 0
u = 0
done = 0

if (p & 1)==1:
print_evens = True
else:
print_evens = False
if (p & 2)==2:
print_odds = True
else:
print_odds = False
if (p & 4)==4:
print_debug = True
else:
print_debug = False

while done==0:
f = gmpy.scan1(a,0) # locate LS 1-bit
if f>0: # it's even
if print_evens:
print a,
a = a >1 # no power division
u += 1
else:
a = a >f # power division
u += f
else:
if print_odds:
print a,
if a==1:
done = 1
seq_end = t + u
else:
a = a*TWE + ONE
t += 1
return [u,t]

>
--
Steven

[Diez B. Roggisch]

Steven D'Aprano schrieb:

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?

I use the logging-module.

Regarding the expensive computations: maysomething like this help:

class DeferredToStrin g(object):

def __init__(self, func):
self.func = func

def __repr__(self):
return repr(self.func( ))

def __str__(self):
return str(self.func() )

dts = DeferredToStrin g

Because then you can do

logger.debug("S ome text for an: %r", dts(lambda: long_computatio n()))

Because AFAIK the string is only interpolated if the logging level is
actually put out.

Diez

[MRAB]

On Sep 2, 5:55*pm, 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?

How about:

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

so that you could then use:

print_("precond ition", level=2)

and:

print_(calculat e_complicated_t hing, level=3)

or:

print_(lambda: calculate_compl icated_thing(ar gument), level=3)

[John Machin]

On Sep 3, 3:52 am, Mensanator <mensana...@aol .comwrote:

On Sep 2, 11:55 am, Steven D'Aprano <st...@REMOVE-THIS-

if (p & 1)==1:
print_evens = True
else:
print_evens = False
if (p & 2)==2:
print_odds = True
else:
print_odds = False
if (p & 4)==4:
print_debug = True
else:
print_debug = False

No, no, no, you've taken "How to write verbose scripts" rather too
literally; try this:

print_evens = p & 1
print_odds = p & 2
print_debug = p & 4

[Mensanator]

On Sep 2, 4:14 pm, John Machin <sjmac...@lexic on.netwrote:

On Sep 3, 3:52 am, Mensanator <mensana...@aol .comwrote:

On Sep 2, 11:55 am, Steven D'Aprano <st...@REMOVE-THIS-

if (p & 1)==1:
print_evens = True
else:
print_evens = False
if (p & 2)==2:
print_odds = True
else:
print_odds = False
if (p & 4)==4:
print_debug = True
else:
print_debug = False

No, no, no, you've taken "How to write verbose scripts" rather too
literally; try this:

print_evens = p & 1
print_odds = p & 2
print_debug = p & 4

Thanks for that. Luckily, the code only does that once per call.

[Bruno Desthuilliers]

John Machin a écrit :

On Sep 3, 3:52 am, Mensanator <mensana...@aol .comwrote:

>On Sep 2, 11:55 am, Steven D'Aprano <st...@REMOVE-THIS-

if (p & 1)==1:
print_evens = True
else:
print_evens = False
if (p & 2)==2:
print_odds = True
else:
print_odds = False
if (p & 4)==4:
print_debug = True
else:
print_debug = False

No, no, no, you've taken "How to write verbose scripts" rather too
literally;

KEYBOARD !

[Uwe Schmitt]

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

[Steven D'Aprano]

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'm currently playing around with a few ideas, one of which is a
decorator to print information about function calls. However, what I'd
like to avoid is having to explicitly call the decorator on every method.
I guess that there's metaclass trickery I can play. Does anyone have any
pointers on how I can apply a decorator to every method in a class
automatically?

--
Steven