This was sent to me as a private reply to a question that I have posted
to python-list@python.org, so I am forwarding it to here.
Chris, please send your messages to the list, and cc the OP.
-------- Original Message --------
Subject: Re: Postfix conditionals
Date: Sun, 5 Jan 2014 14:09:14 -0800
From: Chris Rebert <c...@rebertia.com>
To: Göktuğ Kayaalp <s...@gkayaalp.com>
CC: Python <python-list@python.org>
On Sun, Jan 5, 2014 at 12:24 PM, Göktuğ Kayaalp <s...@gkayaalp.com> wrote:
Hi,
AFAIK, we do not have "postfix conditionals" in Python, i.e. a condition
appended to a
statement, which determines whether the statement runs or not:
py> for i in [False]:
... break if not i
The above piece of code is equivalent to this in Python:
py> for i in [False]:
... if not i
... break
I believe that the first example is superior to the second example when the
two is compared
for readability and intuitiveness.
I'm going to have to disagree. I dislike how this obscures the
if-statement, complicates the language grammar, and adds another
unnecessary way to express the same thing (which violates TOOWTDI)
with little countervailing benefit.
We already have a ternary statement that
looks similar,
py> print('hi') if True else None
Actually, to be pedantic, it's a ternary *expression*. Using it purely
for side-effects (i.e. as a statement) is rather unidiomatic, in the
same way that abusing list comprehensions, e.g.:
[print(i) for i in range(42)]
is frowned upon.
Not to mention that the ternary doesn't work for actual statements
(print() is just a function call in Python 3):
>>> (x = 1) if True else (x = 2)
File "<stdin>", line 1
(x = 1) if True else (x = 2)
^
SyntaxError: invalid syntax
so I reckon there would be no breakage in old code if this kind of syntax
was added. Ruby has
this, and AFAIK Perl also does.
I lack the knowledge of whether the community has opinions on this kind of
notation, so I am
posting this here instead of the ideas list. What are your thoughts on
this?
You can already write:
for i in [False]:
if not i: break
if you feel the need for terseness or a one-liner. Perhaps this
satisfies your desire?
Cheers,
Chris
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