On 2/22/2023 10:42 PM, avi.e.gr...@gmail.com wrote:
That seems like a reasonable if limited use of a semi-colon, Thomas.
Of course, most shells will allow a multi-line argument too like some AWK
scripts I have written with a quote on the first line followed by multiple
lines of properly formatted code and a closing quote.
"Most shells"... got to include cmd.exe, don't forget.
Python though can get touchy about getting just the right amount of
indentation and simple attempts to break your program up into two lines
python -c "import sys
print('\n'.join(sys.path))"
DO not work so well on some shells.
So, yes, I agree. But I tried this on bash under Cygwin on windows using a
"here" document and it worked fine with multiple lines so something to
consider with no semicolons:
$ python <<!
import sys
print('\n'.join(sys.path))
!
/usr/lib/python2.7/site-packages/pylint-1.3.1-py2.7.egg
/usr/lib/python2.7/site-packages/astroid-1.3.4-py2.7.egg
/usr/lib/python2.7/site-packages/six-1.9.0-py2.7.egg
/usr/lib/python27.zip
/usr/lib/python2.7
/usr/lib/python2.7/plat-cygwin
/usr/lib/python2.7/lib-tk
/usr/lib/python2.7/lib-old
/usr/lib/python2.7/lib-dynload
/usr/lib/python2.7/site-packages
/usr/lib/python2.7/site-packages/gtk-2.0
-----Original Message-----
From: Python-list <python-list-bounces+avi.e.gross=gmail....@python.org> On
Behalf Of Thomas Passin
Sent: Wednesday, February 22, 2023 9:05 PM
To: python-list@python.org
Subject: Re: semi colonic
On 2/22/2023 7:58 PM, avi.e.gr...@gmail.com wrote:
Thomas,
This is one of many little twists I see between languages where one
feature impacts use or even the need for another feature.
So can anyone point to places in Python where a semicolon is part of a
best or even good way to do anything?
Mostly I use it to run small commands on the command line with python -c.
e.g.
python -c "import sys;print('\n'.join(sys.path))"
This is handy enough that I wouldn't like to do without.
Another place I use the semicolon (once in a while) is for quick debugging.
I might add as line like, perhaps,
import os; print(os.path.exists(filename))
This way I can get rid of the debugging statement by deleting that single
line. This is non only quicker but I'm less likely to delete too much by
mistake.
Some older languages had simple parsers/compilers that needed some way
to know when a conceptual line of code was DONE and the semi-colon was
a choice for making that clear. But some languages seem to only
continue looking past an end-of-line if they detect some serious
reason to assume you are in middle of something. An unmatched open
parenthesis or square bracket might be enough, and in some languages a
curly brace.
Python mainly has a concept of indentation and blank lines as one part
of the guidance. Continuing lines is possible, if done carefully.
But consider the lowly comma. Some languages may assume more is to
come if it is dangled at the end of a line. But in a language that
supports a dangling comma such as in making a tuple, how is the
interpreter to know more is to come?
a = 5,
a
(5,)
a = 5, \
... 6
a
(5, 6)
Well, one possible use of a semi-colon is to make short one-liner
functions like this:
def twoByFour(a): sq = a*a; forth = sq*sq; return((sq, forth))
There is no reason, of course, that could not be done in multiple
indented lines or other ways.
So if it was allowed in something like a lambda creation, it could be
useful but it isn't!
About the only thing that I can think of is if someone wishes to
compress a file of python code a bit. The indentation can add up but a
semi-colon does not solve all such problems.
Would anything serious break if it was deprecated for use as a
statement terminator? Then again, is it hurting anything? If it
stopped being used this way, could it later be introduced as some new
language feature or operator such as we now have a := b as a reuse of
the colon, maybe a semicolon could be useful at least until someone
decides to allow additional Unicode characters!
Now if there are serious reasons to use semi-colon in python, great.
If not, it is a historical artifact.
-----Original Message-----
From: Python-list
<python-list-bounces+avi.e.gross=gmail....@python.org> On Behalf Of
Thomas Passin
Sent: Wednesday, February 22, 2023 7:24 PM
To: python-list@python.org
Subject: Re: Introspecting the variable bound to a function argument
On 2/22/2023 3:12 PM, Hen Hanna wrote:
On Wednesday, February 22, 2023 at 2:32:57 AM UTC-8, Anton Shepelev
wrote:
Hello, all.
Does Python have an instrospection facility that can determine to
which outer variable a function argument is bound, e.g.:
v1 = 5;
v2 = 5;
do some Python coders like to end lines with ; ?
Very few, probably. It's not harmful but adds unnecessary visual clutter.
def f(a):
print(black_magic(a)) # or
black_magic('a')
f(v1) # prints: v1
f(v2) # prints: v2
the term [call by name] suggests this should be possible.
30 years ago... i used to think about this type of thing A LOT ---
------- CBR, CBV, CBN, (call by value), (call by
name)....
etc.
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