Hi all,
Today I was thinking about a problem I often encounter. Say that I
have (seems I often do!) a deeply nested object, by which I mean
object within object with object, etc.
For example:
x = some.deeply.nested.object.method(some.other.deeply.nested.object.value)
Well, that's extreme but I've worked with code approaching that level
of nested-ness. Now, consider two scenarios:
1. You need to call this thing many times with different arguments, so
you wind up with:
x = some.deeply.nested.object.method(some.other.deeply.nested.object.value1)
y = some.deeply.nested.object.method(some.other.deeply.nested.object.value2)
z = some.deeply.nested.object.method(some.other.deeply.nested.object.value3)
2. You call it inside a loop:
for item in some_iterable:
x =
some.deeply.nested.object.method(some.other.deeply.nested.object.value)
For one thing, I find the long lines unattractive at best and
error-prone at worst, especially if I also have
some.other.deeply.nested.object.method
that I might confuse with the first. To make it look better I might do this:
_o = some.deeply.nested.object
_o.method(_o.value)
which is fine, I suppose.
Then, putting on my company hat, I remembered that, from VBA, you could do this:
with some.deeply.nested.object
.method(.value)
end with
I like the structure of this, since the subordinate block can be
indented, which makes it stand out. Also, it avoids temporary
variables.
So, I was thinking of how to get close to this in Python. I came up
with two approaches:
1.
_o = some.deeply.nested.object
if 1:
_o.method(_o.value)
The "if 1:" forces me to indent the subordinate code, which sets it
apart from the surrounding code. Note that I cannot just
indent because I feel like it since Python is persnickety about indentation.
2.
for _o in [some.deeply.nested.object]:
_o.method(_o.value)
The "for..." sets up the iterator and forces me to indent the subordinate code.
As an aside, approach 1 generates less byte-code since approach 2 sets
up loop machinery which you don't really need in this case.
I have a couple of questions:
1. If you had to choose between approaches 1 and 2, which one would
you go for, and why?
2. What other techniques have you used in such a situation?
--
Gerald Britton
--
http://mail.python.org/mailman/listinfo/python-list
