(I'm replying via Google Groups because I just joined and don't have this thread in my email inbox. It's being a bit flaky so apologies if this comes though twice).
On Jul 26, 5:54 pm, Maxim Khitrov m...@mxcrypt.com wrote:
One of the things I'm trying to address with my library is strict adherence to the current version of the IMAP4 protocol. The other is performance; hence the implementation of extensions such as SASL-IR, IDLE, non-synchronizing literals, multiappend, and compression.
On the performance side, if you have an application that's trying do some sort of processing of a 6 GB mailbox with 700,000 messages in it, executing a separate FETCH command for each message will take you a week to finish. If you try to be clever and FETCH 1000 messages at a time, for example, you'll quickly run into a few problems:
... All are interface design problems, which are inherited by IMAPClient.
P.S. It is not my intention to discourage the use of IMAPClient in any way. Its existence is a good thing for 99% of the users, because it does address a number of key imaplib issues with just the response parser and a UTF-7 codec. My point is that there are real-world use cases out there that cannot be handled by imaplib or IMAPClient, and for those, I'm offering my library as a more general solution that should satisfy the remaining 1% :)
As the maintainer of IMAPClient, I thought I'd weigh in.
I've had a quick look at imaplib2 and I must say it's a solid piece of work. The number of IMAP extensions that it covers is impressive, the iterative streaming of fetch responses is great and the way that concurrent and async commands are handled is quite elegant.
Max is correct about the limitations of imaplib (and therefore IMAPClient). As with many Python libraries (eg. poplib, email, smtplib), data is loaded into memory without the option of streaming (say via generators) and imaplib is not designed with asynchronous handling in mind. This simplicity has benefits in terms of the implementation and usage of the API but it can also lead to problems. I have considered restructuring IMAPClient so that it no longer depends on imaplib and so free it from those inherent limitations. This may still happen.
imaplib2 makes good use of the features available in modern versions of Python. On the other hand, one of my goals with IMAPClient is to support a wide range of Python versions - many newer Python niceties are not used. Python 3 support for IMAPClient is definitely coming but a new addition to our family at home as slowed that effort down somewhat.
I have never considered pushing for IMAPClient to be included as part of the stdlib given that it is fairly easy to install 3rd party packages these days, but I wouldn't be against it. Obviously Python 3 support would have to come first.
I think imaplib2 is a very capable IMAP client library and the Python community could only benefit from having something like it in the standard library (on the proviso, as Brett mentions, that the Python community supports the library by using it widely).
Here's a few comments about imaplib2 from my own biased perspective:
It requires too much effort on behalf of the caller. Your example.py highlights how datetimes are returned as strings that need to be converted to real datetimes and FETCH response keys need to be uppercased to ensure consistency. The need to jump through the same non-trivial hoops each time I used imaplib was one of the frustrations that led to the creation of IMAPClient. Please consider having imaplib2 do a little more work so that every user doesn't have to.
Similarly, UID support could be better. IMAPClient has a boolean attribute which lets you select whether you want UIDs to be transparently used for future commands. Having to specify whether you want UID support enabled on each call is a little clumsy. It's unlikely that a user of imaplib2 would want to toggle between using UIDs and not on every call.
This has already been mentioned but imaplib2 won't get accepted into the stdlib if you don't conform to PEP 8. Those tabs have to go.
How much testing has imaplib2 seen against real IMAP implementations? Throughout IMAPClient's history its users have found many unexpected behaviours in various popular IMAP implementations. Those discoveries have lead to updates to IMAPClient's code and tests (this is the "battle-tested" aspect that Michael refers too). On top of its unit tests, IMAPClient has a fairly extensive live test script that can be run (destructively) against a real IMAP account. I have test accounts with a number of different IMAP implementations which I regularly test IMAPClient against. A set of "live" tests is invaluable for testing new features and avoiding regressions between versions. It would be interesting to see what problems you find if you set up something similar for imaplib2.
Anyway, I wish you all the best with your project.
 - Are you aware there's already another project with the same name? http://www.janeelix.com/piers/python/imaplib2.html