Hello World

[Cameron Simpson]

On 21Dec2014 01:31, Terry Reedy <tjreedy at udel.edu> wrote:
>On 12/21/2014 12:31 AM, Chris Angelico wrote:
>>On Sun, Dec 21, 2014 at 4:14 PM, CM <cmpython at gmail.com> wrote:
>>>I ran it in IDLE with Python 2.7.8 and got:
>>>
>>>Traceback (most recent call last):
>>>   File "C:/Python27/helloworld.py", line 39, in <module>
>>>     lambda _, __, ___, ____, _____, ______, _______, ________: _
>>>   File "C:/Python27/helloworld.py", line 21, in <lambda>
>>>     _))) + (_____ << ______) + (_ << ___)
>>>OSError: [Errno 9] Bad file descriptor
>>
>>Yes, because - like most "Hello world" programs - it attempts to write
>>to stdout. This interferes with IDLE and the way it captures output
>>for the graphical environment.
>
>Just to be clear, writing to sys.stdout works fine in Idle.
>>>> import sys; sys.stdout.write('hello ')
>hello  #2.7
>
>In 3.4, the number of chars? bytes? is returned and written also.
>
>Whether you mean something different by 'stdout' or not, I am not 
>sure.

He means file descriptor 1. sys.stdout does not have a file descriptor at all 
under IDLE.

>The error is from writing to a non-existent file descriptor.
>The os 'file descriptor functions are unix functions.  Many but not 
>all also work on Windows.  I do not believe that was true on msdos. 
>According to the os doc, they do not work on osx.

Please cite that doc. OSX _is_ UNIX, like almost all modern platforms.
A glance at a set of 3.4.0 docs convenient to hand finds only one call 
explicitly labelled as not working under MacOS (os.fdatasync).

>Python io streams are not required to have a file descriptor.

Indeed, but the program cited relies on one. So it is not perfectly portable, 
but still widely usable.

Cheers,
Cameron Simpson <cs at zip.com.au>

Tachyon: A gluon that's not completely dry.