Comments on Version 2, Draft Pep for Deprecating Builtins

[Duncan Booth]

holger krekel <pyth at devel.trillke.net> wrote in 
news:mailman.1020082610.7467.python-list at python.org:

> Btw, what is the best/shortest way to express 'filter' and 'reduce' with 
> list comprehensions?

 filter(fn, lst)
becomes:
 [ v for v in lst if fn(v) ]

 filter(None, lst)
becomes:
 [ v for v in lst if v ]

If the second argument to filter is a string or tuple then you have to 
convert the resulting list back to the appropriate type:

e.g.
 filter(fn, aString)
 str.join('', [ v for v in aString if fn(v) ])

reduce doesn't return a list, so a list comprehension is not an appropriate 
replacement.

 reduce(fn, seq, initial)
becomes:
 res = initial
 for v in seq: res = fn(res, v)

All of these replacements are big winners if they remove a use of the 'l' 
word. I don't think any of them lose in clarity even if there are no 'l's 
around.
 
-- 
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?