Re: [Python-Dev] TextIO seek and tell cookies

2016-09-26 Thread Guido van Rossum
Yeah, that should work. The implementation is something like a byte offset to the start of a line plus a character count, plus some misc flags. I found this implementation in the 2.6 code (the last version where it was pure Python code): def _pack_cookie(self, position, dec_flags=0,

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-26 Thread Greg Ewing
Ben Leslie wrote: But the idea of transmitting these offsets outside of a running process is not something that I had anticipated. It got me thinking: is there a guarantee that these opaque values returned from tell() is stable across different versions of Python? Are they even guaranteed to

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-26 Thread Random832
On Mon, Sep 26, 2016, at 05:30, Ben Leslie wrote: > I think the case of JSON or SQL database is even more important though. > > tell/seek can return 129-bit integers (maybe even more? my maths might > be off here). > > The very large integers that can be returned by tell() will break >

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-26 Thread Ben Leslie
It was pointed out in private email that technically JSON can represent very large integers even if ECMAScript itself can't. But the idea of transmitting these offsets outside of a running process is not something that I had anticipated. It got me thinking: is there a guarantee that these opaque

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-26 Thread Ben Leslie
I think the case of JSON or SQL database is even more important though. tell/seek can return 129-bit integers (maybe even more? my maths might be off here). The very large integers that can be returned by tell() will break serialization to JSON, and storing in a SQL database (at least for most

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-26 Thread Ben Leslie
On 25 September 2016 at 17:21, MRAB wrote: > On 2016-09-26 00:21, Ben Leslie wrote: >> >> Hi all, >> >> I recently shot myself in the foot by assuming that TextIO.tell >> returned integers rather than opaque cookies. Specifically I was >> adding an offset to the value

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-25 Thread Peter Ludemann via Python-Dev
On 25 September 2016 at 21:18, Guido van Rossum wrote: > Be careful though, comparing these to plain integers should probably > be allowed, ​There's a good reason why it's "opaque" ... why would you want to make it less opaque? And I'm curious why Python didn't adopt the

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-25 Thread Guido van Rossum
Be careful though, comparing these to plain integers should probably be allowed, and we also should make sure that things like serialization via JSON or storing in an SQL database don't break. I personally think it's one of those "learn not to touch the stove" cases and there's limited value in

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-25 Thread Nick Coghlan
On 26 September 2016 at 10:21, MRAB wrote: > On 2016-09-26 00:21, Ben Leslie wrote: >> Are there any downsides to this? I've made some progress developing a >> patch to change this functionality. Is it worth polishing and >> submitting? >> > An alternative might be a

Re: [Python-Dev] TextIO seek and tell cookies

2016-09-25 Thread MRAB
On 2016-09-26 00:21, Ben Leslie wrote: Hi all, I recently shot myself in the foot by assuming that TextIO.tell returned integers rather than opaque cookies. Specifically I was adding an offset to the value returned by TextIO.tell. In retrospect this doesn't make sense/ Now, I don't want to

[Python-Dev] TextIO seek and tell cookies

2016-09-25 Thread Ben Leslie
Hi all, I recently shot myself in the foot by assuming that TextIO.tell returned integers rather than opaque cookies. Specifically I was adding an offset to the value returned by TextIO.tell. In retrospect this doesn't make sense/ Now, I don't want to drive change simply because I failed to read