'with' statement in python ?

[Duncan Booth]

asgard <asgard at hellnet.cz> wrote in news:mailman.993497019.14391.python-
list at python.org:

> could be written as
> 
> with self:
>     a=1
>     b=2
> 
> ? Of course it would work with other names too.
> 
Does this mean "self.a=1; self.b=2" or are either of a and b local or 
global variables?

There are two main uses for with. In your example you are using with simply 
to avoid writing 'self.' in front of each member reference. The problem is 
that in Python you cannot tell until runtime whether self has attributes a 
and b. You could assume that all variable references inside the 'with' 
became prefixed with 'self.', but then you couldn't access any values that 
weren't in your object. So simply as a way to save yourself typing 'with' 
won't work.

The other use for with is to precalculate some complicated reference:
    with some.thing[or](other):
        foo = 5 * bar
        bar += 1
Python already has an equivalent way to do this:
    t = some.thing[or](other)
    t.foo = 5 * t.bar
    t.bar += 1
       

-- 
Duncan Booth                                             duncan at rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?