On 17Feb2015 13:21, candide <c.cand...@laposte.net> wrote:
Official Python documentation very frequently invokes a mysterious *container* data structure. The PLR manual explains : -------------------------- Some objects contain references to other objects; these are called containers. --------------------------
And this is the basic thing, as you understand.
So containers contain : what a great definition!
Shrug. It is a useful descriptive term when you want to talk about things. You might keep in mind that a "container"'s _primary_ purpose is usually its containing function. So a list. But not so some arbitrary object, even though most objects have references to other objects.
[...]
So I was considering a Python range object NOT being a container: indeed, range(10**6) does NOT store 10**6 integers and range(10**6) has a small memory footprint
[...]
Then, mining the official docs, I realized that the collections module provides an ABC Container class allowing you to know if a given object is a container or not. And what a surprise, a range object IS a container !
You might find it duck types like other containers. [...]
The docs at : https://docs.python.org/3.2/reference/datamodel.html#object.__contains__ explains that a container is an object compatible with the membership test (in and not in operators).
Duck typing again: this bases the term on behaviour, not memory use.
So a file is a container ? recall a file supports the in operator :
Yes and no. A file can be iterated. "in" on a file reads the file as a side effect of iterating over it. A generator also supports "in", again by iteration.
Neither of these things has a .__contains__ method; the "in" operator falls back to iteration if there is no .__contains__.
A container usually lets you test "in" in a nondestructive/nonconsuming fashion. An iterable can be "in"ed, but it will be consumed. So iterables are not, of themselves, containers.
So, range? A range object knows its bounds and state; it can answer "in" without consuming the range iteration, so it is effectively a container.
Hoping this helps. Cheers, Cameron Simpson <c...@zip.com.au> [Alain] had been looking at his dashboard, and had not seen me, so I ran into him. - Jean Alesi on his qualifying prang at Imola '93 -- https://mail.python.org/mailman/listinfo/python-list
