On 2012-01-13, Devin Jeanpierre <jeanpierr...@gmail.com> wrote: > On Fri, Jan 13, 2012 at 10:13 AM, Grant Edwards <invalid@invalid.invalid> > wrote: >> On 2012-01-13, Devin Jeanpierre <jeanpierr...@gmail.com> wrote: >>> On Fri, Jan 13, 2012 at 7:30 AM, Chris Angelico <ros...@gmail.com> wrote: >>>> It seems there's a distinct difference between a+=b (in-place >>>> addition/concatenation) and a=a+b (always rebinding), which is sorely >>>> confusing to C programmers. But then, there's a lot about Python >>>> that's sorely confusing to C programmers. >>> >>> I think this is confusing to just about everyone, when they first >>> encounter it. >> >> That depends on what languages they've used in the past and whether >> they skip reading any documentation and just assume that all languages >> work the same way. >> >> I would agree that for the majority of new users, they previously used >> only languages where an assignment operator does a "copy value", and >> that 90+ percent of the time those new users they assume all languages >> work that way. > > That isn't what I was referring to. Specifically, it confuses > almost everyone the first time they encounter it that "a += b" > is not the same as "a = a + b".
If you've ever implemented operator=, operator+, and operator+= in C++ you'll know how and why they are different. A C++ programmer would be wondering how either can work on immutable objects, and that's where Python's magical rebinding semantics come into play. -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
