从文本表示重构Python对象

Question

Is it possible to create an object from the represented text of python objects when they are repr esented on the screen?

>>> select.select([s], [],[])
([<socket._socketobject object at 0x7f274914c600>], [], [])
>>> eval('<socket._socketobject object at 0x7f274914c600>') # Fail

Or once the object is represented to stdout, does it get GCd?

Not of significant use, but when playing with the Python CLI, it might be occasionally helpful.

Answer 1

The output of repr may be able to reconstruct the object, however the convention is, if it has bits surrounded by angle brackets then those bits aren't reconstructible.

So in this case you can't reconstruct the socket, and yes it will be garbage collected straight away.

Answer 2

It is not, as apparently text presentation does not necessarily contain all information of the object.

If you want to text-like object representation try JSON module.

http://docs.python.org/library/json.html?highlight=json#json

Also please note that objects encapsulated in this presentation cannot have native object bindings, like sockets, file handles, etc.

Answer 3

You are encouraged to create objects for which the repr allows you to create a new object by pasting the repr output, but it is not strictly enforced. Depending on the nature of the object and any internals, this also might not be something that is easy to do.

There are many ways to do it. Here is a very simple example of one way:

class ReprObject(object):
    def __init__(self, value, item):
        self.value = value
        self.item = item

    def __repr__(self):
        return '%s(**%r)' % (self.__class__.__name__, self.__dict__)

So then we take that to the interactive interpreter and create an instance:

>>> r = ReprObject(value=1, item=True)
>>> r
ReprObject(**{'item': True, 'value': 1})

Now copy/paste that repr and use it to create a new object:

>>> r2 = ReprObject(**{'item': True, 'value': 1})
>>> r2
ReprObject(**{'item': True, 'value': 1})

And eval() would also work:

>>> eval(repr(r2))
ReprObject(**{'item': True, 'value': 1})