On Tue, 23 Feb 2010 05:48:09 -0800, Mark Dickinson wrote: > On Feb 23, 8:11 am, Steven D'Aprano > <ste...@remove.this.cybersource.com.au> wrote: >> Making spaces significant in that fashion is mind-bogglingly awful. >> Let's look at a language that does this: >> >> [st...@sylar ~]$ cat ws-example.rb >> def a(x=4) >> x+2 >> end >> >> b = 1 >> print (a + b), (a+b), (a+ b), (a +b), "\n" >> >> [st...@sylar ~]$ ruby ws-example.rb >> 7773 > > Hmm. That's pretty nasty, all right. Not that Python can claim to be > immune to such behaviour: > >>>> 3 .real > 3 >>>> 3. real > File "<stdin>", line 1 > 3. real > ^ > SyntaxError: invalid syntax > > > Though the fact that one of the cases raises an exception (rather than > silently giving some different behaviour) ameliorates things a bit.
It ameliorates it *completely* -- you won't get silent errors in Python because you add or delete whitespace around a dot. "I find it amusing when novice programmers believe their main job is preventing programs from crashing. ... More experienced programmers realize that correct code is great, code that crashes could use improvement, but incorrect code that doesn't crash is a horrible nightmare." http://www.pphsg.org/cdsmith/types.html The edge case occurs because dot does double-duty as an operator and as part of float literals. However, float literals never include whitespace: >>> 1.5 1.5 >>> 1 . 5 File "<stdin>", line 1 1 . 5 ^ SyntaxError: invalid syntax and likewise for 1. 5 and 1 .5 -- the only way to get a float literal with a decimal point is by not including whitespace in it. So there is never any ambiguity about floats. You can even do this: >>> 1.5.__str__() '1.5' And since . is an operator outside of float literals, you can do this: >>> import sys >>> sys . platform 'linux2' although why you'd want to escapes me :) This actually is a feature, since it is useful when calling methods on int literals. However this is a very rare thing to do. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
