clist has a bug that limits how a clist instance can be used.

[Ray C Horn]

clist uses the following method however __repr__ methods must take care to use some method other than the str() method when producing a representation of a clist because the method below causes stack overflow problems at runtime.

    def __repr__(self):
        return "clist(%s)" %str(self)

A better method would be to represent the clist as a list of items rather than as a representation of the whole list.

This bug affects how clist instances get handled by a method that needs to represent the clist - this does not happen often however when it does happen the method above fails.

The reason is str() uses __repr__() - this is common for all Python objects that seek to use str() to form a representation of an object where the item being rendered by str() is the object itself.

[Ray C Horn (mrpython94596)]

Try this instead:

    def __repr__(self):
        return "clist(%s)" % (','.join([str(item) for item in self]))

This method fails whenever any items in a clist happens to be a clist instance.

[Kevin Shuk (surf)]

Thank you for the report & suggested fix. I did not realise the bit about str() using __repr__() - learn something new every day!

My plan is to come up with a test case that shows the broken behavior, then apply your suggested fix and merge into trunk as soon as possible.

[Ray C Horn (mrpython94596)]

I have run into the str() and __repr__() problem many times while coding my
huge (125,000+ lines) library of reusable code and I have had to code around
it by ensuring I never issue a str() during a __repr__() when the result can
be recursive.

See also the following from a quick Google search:

[Python-3000] PEP: str(container) should call str(item), not repr ... -->
http://mail.python.org/pipermail/python-3000/2008-May/013876.html

http://www.google.com/search?rlz=1C1GGLS_enUS291US304&sourceid=chrome&ie=UTF-8&q=str+and+__repr__+for+python

Enjoy. :-)

--------------------------------------------------
From: "Kevin Shuk" <email address hidden>
Sent: Thursday, January 22, 2009 2:37 PM
To: <email address hidden>
Subject: [Bug 319792] Re: clist has a bug that limits how a clist instance
canbe used.

> Thank you for the report & suggested fix. I did not realise the bit
> about str() using __repr__() - learn something new every day!
>
> My plan is to come up with a test case that shows the broken behavior,
> then apply your suggested fix and merge into trunk as soon as possible.
>
> ** Changed in: pyax
> Importance: Undecided => Medium
> Assignee: (unassigned) => Kevin Shuk (surf)
> Status: New => In Progress
>
> --
> clist has a bug that limits how a clist instance can be used.
> https://bugs.launchpad.net/bugs/319792
> You received this bug notification because you are a direct subscriber
> of the bug.
>
> Status in Salesforce.com Apex API library for Python: In Progress
>
> Bug description:
> clist uses the following method however __repr__ methods must take care to
> use some method other than the str() method when producing a
> representation of a clist because the method below causes stack overflow
> problems at runtime.
>
>
> def __repr__(self):
> return "clist(%s)" %str(self)
>
> A better method would be to represent the clist as a list of items rather
> than as a representation of the whole list.
>
> This bug affects how clist instances get handled by a method that needs to
> represent the clist - this does not happen often however when it does
> happen the method above fails.
>
> The reason is str() uses __repr__() - this is common for all Python
> objects that seek to use str() to form a representation of an object where
> the item being rendered by str() is the object itself.
>

[Kevin Shuk (surf)]

Committed to trunk rev 63