Keith Devens .com - Weblog: Reference identity in PHP and Python

Thursday, February 20, 2003

Reference identity in PHP and Python

Question: Is it possible to find out if two references point to the same thing in PHP and Python?

I know in Java you can just compare the references directly: a == b will tell you.

I know in C/C++ you can just compare pointer memory addresses: a == b will tell you.

I know in Perl you can stringify a reference and compare the resulting strings, since a stringified reference contains the memory address.

Ruby has object.equal?, etc. etc. I'm not quite sure about things like VB/VBscript and Javascript right now.

Anyway, the point is, references are pretty seamless in Python and PHP. Is there any way to find out that two variables aren't just equal, but point to the same thing?

Permalink | 1 Comment | Tags: Programming | id 3479

18:04 (utc-5)

Comments

Adam Vandenberg wrote:

Python has the "is" operator for testing object identity.
By far the most common use of is / is not I've seen is testing an object against the singleton "None":

if stuff is not None:
# do something

∴ Adam Vandenberg | 21-Feb-2003 12:03pm est | #1478

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