Weatherby,
Of course you are right and people can, and do, discuss whatever they feel like.
My question is a bit more about asking if I am missing something here as my
personal view is that we are not really exploring in more depth or breadth and
are getting fairly repetitive as if in a typical SF time loop. How does one
break out?
Languages often change and people do come and go so some topics can often be
re-opened. This though is a somewhat focused forum and it is legitimate to ask
if a conversation might best be taken elsewhere for now. The main focus is, at
least in theory, aspects of python and mostly about the core as compared to
very specific modules, let alone those nobody here has ever even used. Within
that, it is fair at times to compare something in python to other languages or
ask about perceived bugs or about possible future enhancements. We could
discuss if "YIELD FROM" is just syntactic sugar as it often can be done with
just the naked YIELD statement, or whether it really allows you to do
innovative things, as an example.
But I think where this conversation has gone is fairly simple. The question was
why print() does not return the number of characters printed. The answers
boiled down to that this was not the design chosen and is mostly consistent
with how python handles similar functions that return nothing when the change
is largely "internal" in a sense. In addition, plenty of us have suggested
alternate ways to get what the OP asked for, and also pointed out there are
other things that someone may have wanted instead or in addition, including the
actual number of bytes generated for encodings other than vanilla ASCII, or
pixels if the text was rendered on a screen using variable width fonts and so
on.
Some of the above already counted, in my mind, as adding depth or breadth to
the original question. But if the conversation degrades to two or more sides
largely talking past each other and not accepting what the other says, then
perhaps a natural ending point has been reached. Call it a draw, albeit maybe a
forfeit.
So, as part of my process, I am now stuck on hearing many questions as valid
and others as not productive. I don't mean just here, but in many areas of my
life. The answer is that historically, and in other ways, python took a
specific path. Others took other paths. But once locked into this path, you run
into goals of trying to remain consistent and not have new releases break older
software or at least take time to deprecate it and give people time to adjust.
I have seen huge growing pains due to growth. An example is languages that have
added features, such as promises and their variants and used them for many
purposes such as allowing asynchronous execution using multiple methods or
evaluating things in a more lazy way so they are done just in time. Some end up
with some simple function call being augmented with quite a few additional
functions with slightly different names and often different arguments and ways
they are called that mostly should no longer be mixed with other variants of
the function. You need compatibility with the old while allowing the new and
then the newer and newest.
Had the language been built anew from scratch, it might be simpler and also
more complex, as they would skip the older versions and pretty much use the
shinier new version all the time, even as it often introduces many costs where
they are not needed.
So it can be very valid to ask questions as long as you also LISTEN to the
answers and try to accept them as aspects of reality. Yes, python could have
had a different design and perhaps someday may have a different design. But
that is not happening TODAY so for today, accept what is and accept advice on
how you might get something like what you want when, and if, you need it. The
goal often is to get the job done, not to do it the way you insist it has to be
done.
At some point, unless someone has more to say with some new twist, it does
become a bit annoying.
So let me say something slightly new now. I have been reading about interesting
uses of the python WITH statement and how it works. Some of the examples are
creating an object with dunder methods that get invoked on entry and exit that
can do all kinds of things. One is the ability to modify a list in a way that
can be rolled back if there is an error and it is quite simple. You make a copy
of the original list on entry. Things are then done to the copy. And if you
exit properly, you copy the modified list back on top of the original list.
Errors that result simply unwind the serious of transactions by leaving the
original list untouched.
Another example has your output stream redirected within the WITH and then put
back in place after. What this allows, among many things, is for everything
printed to be desrever. Now clearly, such a technique could also be used to
capture what is going to be printed, and count how many bytes or characters it
produced and make the result available after you exit the region. Heck, if fed
a paragraph of text, it could not only print it but create one or more objects
containing a detailed analysis including guessing what language it is in,
translating it to English, pointing out spelling and grammar errors, and
mailing you a copy! You can imagine quite a few side effects of calling print()
but again, why would you put the functionality within print() versus in a
function you wrote that does all that as well as calling print()?
But even assuming you code that properly and rewrite all your code as something
like:
with capture:
print(...)
# use chars_written_within_width as a variable created within that holds what
you want.
Is that really any better than several other ways we have suggested would work
such as creating an f-string independently and then printing it which would
handle quite a few use cases?
If others wish to keep debating this topic or enhancing it, fine. I am not
judging but simply expressing the personal opinion that even if I might have
more to add, I am not motivated to do so any longer. Then again, I may soon
lose the motivation to be part of this forum and take up other hobbies 😉
-----Original Message-----
From: Python-list <[email protected]> On
Behalf Of Weatherby,Gerard
Sent: Monday, February 13, 2023 10:16 AM
To: [email protected]
Subject: Re: evaluation question
“Why are we even still talking about this?”
Because humans are social creatures and some contributors to the list like to
discuss things in depth.
From: Python-list <[email protected]> on
behalf of [email protected] <[email protected]>
Date: Friday, February 10, 2023 at 6:19 PM
To: [email protected] <[email protected]>
Subject: RE: evaluation question
*** Attention: This is an external email. Use caution responding, opening
attachments or clicking on links. ***
There are no doubt many situations someone wants to know how long something
will be when printed but often at lower levels.
In variable-width fonts, for example, the number of characters does not really
line up precisely with how many characters. Some encodings use a varying number
of bytes and, again, the width of the output varies.
So for people who want to make 2-D formatted output like tables, or who want to
wrap lines longer than N characters, you more often let some deeper software
accept your data and decide on formatting it internally and either print it at
once, when done calculating, or in the case of some old-style terminals, use
something like the curses package that may use escape sequences to update the
screen more efficiently in various ways.
If someone wants more control over what they print, rather than asking the
print() function to return something that is mostly going to be ignored, they
can do the things others have already suggested here. You can make your message
parts in advance and measure their length or anything else before you print. Or
make a wrapper that does something for you before calling print, perhaps only
for common cases and then returns the length to you after printing.
I wonder if the next request will be for print() to know what your output
device is and other current settings so it return the width your text takes up
in pixels in the current font/size ...
I add a tidbit that many ways of printing allow you to specify the width you
want something printed in such as you want a floating point value with so many
digits after the decimal point in a zero or space padded field on the left. So
there are ways to calculate in advance for many common cases as to how long
each part will be if you specify it. Besides, I am not really sure if "print"
even knows easily how many characters it is putting out as it chews away on the
many things in your request and calls dunder methods in objects so they display
themselves and so on. I assume it can be made to keep track, albeit I can
imagine printing out an APL program with lots of overwritten characters where
the number of bytes sent is way more than the number of spaces in the output.
Why are we even still talking about this? The answer to the question of why
print() does not return anything, let alone the number of characters printed,
is BECAUSE.
-----Original Message-----
From: Python-list <[email protected]> On
Behalf Of Python
Sent: Friday, February 10, 2023 4:56 PM
To: [email protected]
Subject: Re: evaluation question
On Sat, Feb 11, 2023 at 08:30:22AM +1100, Chris Angelico wrote:
> On Sat, 11 Feb 2023 at 07:36, Python <[email protected]> wrote:
> > You would do this instead:
> >
> > message = f"{username} has the occupation {job}."
> > message_length = len(message)
> > print(message)
> > print(message_length)
> > ...
> >
>
> It's worth noting WHY output functions often return a byte count. It's
> primarily for use with nonblocking I/O, with something like this:
>
> buffer = b".............."
> buffer = buffer[os.write(fd, buffer):]
>
> It's extremely important to be able to do this sort of thing, but not
> with the print function, which has a quite different job.
I would agree with this only partially. Your case applies to os.write(), which
is essentially just a wrapper around the write() system call, which has that
sort of property... though it applies also to I/O in blocking mode,
particularly on network sockets, where the number of bytes you asked to write
(or read) may not all have been transferred, necessitating trying in a loop.
However, Python's print() function is more analogous to C's printf(), which
returns the number of characters converted for an entirely different reason...
It's precisely so that you'll know what the length of the string that was
converted is. This is most useful with the
*snprintf() variants where you're actually concerned about overrunning the
buffer you've provided for the output string, so you can realloc() the buffer
if it was indeed too small, but it is also useful in the context of, say, a
routine to format text according to the size of your terminal. In that context
it really has nothing to do with blocking I/O or socket behavior.
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