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what's the big deal for print()

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  what's the big deal for print() pipehappy <pipehappy@gmail.com> - 2011-06-24 19:39 -0700
    Re: what's the big deal for print() John Gordon <gordon@panix.com> - 2011-06-25 03:23 +0000
      Re: what's the big deal for print() steve+comp.lang.python@pearwood.info - 2011-06-25 14:01 +1000
        Re: what's the big deal for print() Duncan Booth <duncan.booth@invalid.invalid> - 2011-06-27 08:23 +0000
    Re: what's the big deal for print() Terry Reedy <tjreedy@udel.edu> - 2011-06-24 23:54 -0400

#8427 — what's the big deal for print()

Hi,

Why people want print() instead of print str? That's not a big deal
and the old choice is more natural. Anyone has some clue?

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#8429

In <d3558c5d-0fe6-4da7-843d-c2f45b2bf869@y13g2000yqy.googlegroups.com> pipehappy <pipehappy@gmail.com> writes:

> Why people want print() instead of print str? That's not a big deal
> and the old choice is more natural. Anyone has some clue?

Because the new Python uses print().  print "str" is the old way.

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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#8432

John Gordon wrote:

> In <d3558c5d-0fe6-4da7-843d-c2f45b2bf869@y13g2000yqy.googlegroups.com>
> pipehappy <pipehappy@gmail.com> writes:
> 
>> Why people want print() instead of print str? That's not a big deal
>> and the old choice is more natural. Anyone has some clue?
> 
> Because the new Python uses print().  print "str" is the old way.


I think you missed the point of the question, which is, *why* does the new
Python (version 3+) use a function print() instead of a statement?

The problems with print as a statement includes:

It requires special treatment in the compiler, instead of just being an
ordinary function like len(), etc.

It's hard to come up with special syntax to add extra functionality to print
statement. Compare the ugly syntax needed to add support for printing to
writable files in Python 2:

    print >>fileobj, arg  # what does the mysterious >> syntax mean?

compared to the natural way it works in Python 3:

    print(arg, file=fileobj)

Likewise, changing the delimiter between arguments. Python 3 has:

    >>> print(1, 2, 3, sep="*")
    1*2*3

while Python 2 requires you to generate the string by hand, and then print
it:

    >>> print '*'.join('%s' % x for x in (1, 2, 3))
    1*2*3


One Frequently Asked Question is "How do I get rid of the newline after
printing?" In Python 2, you leave a comma at the end of the print
statement. What? A comma? How does that make *any* sense at all???
Unfortunately, while that gets rid of the newline, it also leaves spaces
between items:

>>> def example():
...     print 1,
...     print 2,
...     print 3
...
>>> example()
1 2 3

Here's the Python 3 version:

>>> def example():
...     print(1, sep='', end='')
...     print(2, sep='', end='')
...     print(3, sep='')
...
>>> example()
123


To get the same result in Python 2, you have to use sys.stdout.write().


The canonical explanation for why print is now a function is here:

http://www.python.org/dev/peps/pep-3105/




-- 
Steven

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#8498

steve+comp.lang.python@pearwood.info wrote:

> Unfortunately, while that gets rid of the newline, it also leaves 
spaces
> between items:
> 
>>>> def example():
> ...     print 1,
> ...     print 2,
> ...     print 3
> ...
>>>> example()
> 1 2 3
> 
> Here's the Python 3 version:
> 
>>>> def example():
> ...     print(1, sep='', end='')
> ...     print(2, sep='', end='')
> ...     print(3, sep='')
> ...
>>>> example()
> 123
> 
> 
> To get the same result in Python 2, you have to use sys.stdout.write
().
> 

That isn't entirely true: you could set the `softspace` attribute on 
sys.stdout, but that is even messier.

>>> def foo():
...     print 1,
...     sys.stdout.softspace=0
...     print 2,
...     sys.stdout.softspace=0
...     print 3
...
>>> foo()
123

-- 
Duncan Booth http://kupuguy.blogspot.com

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#8430

On 6/24/2011 10:39 PM, pipehappy wrote:
> Hi,
>
> Why people want print() instead of print str? That's not a big deal
> and the old choice is more natural. Anyone has some clue?

print as a function instead of a statement is consistent with input as a 
function, can be overridden with custom versions, can be passed to 
functions as an argument, and can have options passed as arguments 
instead of with terrible syntax hacks.

-- 
Terry Jan Reedy

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