(If you receive this twice, please excuse the duplicate email.
User-error on my part, sorry.)
On Wed, 28 May 2008 08:23:38 am Raymond Hettinger wrote:
> A flatten() implementation doesn't really care about whether
> an input is a string which supports all the string-like methods
> such as capitalize(). Wouldn't it be better to write your
> version of flatten() with a registration function so that a user
> could specify which objects are atomic? Otherwise, you
> will have to continually re-edit your flatten() code as you
> run across other non-stringlike objects that also need to
> be treated as atomic.
Just throwing a suggestion out there...
def atomic(obj, _atomic=(basestring,)):
try:
return bool(obj.__atomic__)
except AttributeError:
if isinstance(obj, _atomic):
return True
else:
try:
iter(obj)
except TypeError:
return True
return False
assert atomic("abc")
assert not atomic(['a', 'b', 'c'])
If built-in objects grew an __atomic__ attribute, you could simplify the
atomic() function greatly:
def atomic(obj):
return bool(obj.__atomic__)
However atomic() is defined, now flatten() is easy:
def flatten(obj):
if atomic(obj):
yield obj
else:
for item in obj:
for i in flatten(item):
yield i
If you needed more control, you could customise it using standard
techniques e.g. shadow the atomic() function with your own version,
sub-class the types you wish to treat differently, make __atomic__ a
computed property instead of a simple attribute, etc.
Re-writing the above to match Python 3 is left as an exercise.
--
Steven
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