[Python-Dev] PEP 3144: IP Address Manipulation Library for the Python Standard Library (original) (raw)

Peter Moody peter at hda3.com
Wed Aug 19 17:19:46 CEST 2009

On Wed, Aug 19, 2009 at 6:47 AM, Tino Wildenhain<tino at wildenhain.de> wrote:

Antoine Pitrou wrote:

Le Tue, 18 Aug 2009 13:00:06 -0700, Peter Moody a écrit :

Howdy folks, I have a first draft of a PEP for including an IP address manipulation library in the python stdlib. It seems like there are a lot of really smart folks with some, ahem, strong ideas about what an IP address module should and shouldn't be so I wanted to solicit your input on this pep. When you say : « the results of the first computation should be cached and only re-generated should the object properties change » does it mean that the objects are mutable? Would it make sense to make them immutable and therefore hashable (such as, e.g., datetime objects)? They could impelement hash to behave correctly in this case. In the examples however I see: o.broadcast  IPv4Address('1.1.1.255') this is often used but not the only valid broadcast address, in fact, any address between network address and max(address with given netmask) can be defined as broadcast. Maybe biggest or greatest would be better name for the attribute. User is then free to interpret it as broadcast if desired. The attribute network returned as address object also does not seem right.

by convention, the highest address in a given network is called the broadcast address while the lowest address is called the network address. They're also distinct addresses, as opposed to networks, hence .broadcast/.network/etc returning IPvXAddress objects. calling them .biggest and .smallest would be confusing.

am I misinterpreting what you mean?

The performance hit you mention by translating the object upfront is neglegtible I'd say - for any sensible use of the object you'd need the binary form anyway. You can even use system (e.g. socket) funtions to make the translation very fast. This also safes space and allow vor verification of the input.

I'll look into using socket where I can, but the computational hit actually wasn't negligible. A common use for something like this library might be to verify that an addresses typed by a user is valid, '192.168.1.1' instead os '1921.68.1.1'; computing the extra attributes delays the return time and doesn't actually benefit the user or programmer.

Cheers, /peter

(e.g. '255.255.255.255/32' is 18 bytes where it could  be stored as 8 bytes instead (or even 5 if you use ip/prefixlength)

I have a very very old implementation which even did the translation from cidr format to integer in python code (I don't say plain ;) but maybe worth a look: http://www.zope.org/Members/tino/IPPatternAuthentication/IPHelper.py/view Regards Tino

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