Skip to main content

Brett Cannon: Clarifications on LINQ

Brett Cannon: Clarifications on LINQ: "Calvin Spealman set me straight on the true importance of LINQ."

Well, what an interesting start to an article in my news reader. Yes, I am Calvin Spealman. Brett goes on to talk about some details of this, mostly repeating and rephrasing what I set him straight on (his words, not mine), in reguards to LINQ.

Although we can not, at this time, get the AST for any expressions or blocks prior to compilation, I don't expect or see how or why we would reach this at Python 2.6, either. Firstly, I don't see how python would no to not-compile anything without some special "this is meant to be used just for its AST" syntax. Secondly, I doubt it would be any cheaper to generate the AST without compiling it into bytecode, after factoring in the time it might take to figure out if you need to do so or not. The most likely and efficient way will probably be the most obvious, in this case: pass a function object, built with def or lambda, but expressions by themselves (ie, not lambdas) will be pretty unusable. Anything else would require some kind of mechanism to know that a parameter expects AST, and that would break the python function model. So, barring anything along the lines of function decorators that say "parameter 3 gets the expression's AST" and hooks in the function call mechanism to catch this sort of thing, I don't see the direction of the Python 2.6 comment. Besides, anything along those lines seems like it would pose some serious security risks.

Am I misunderstanding the statement?

Comments

Anonymous said…
You can get pretty far by passing objects into a lambda that override all operators, attribute access and so on, to find out what the lambda "does" inside with it's parameters. This can be used to build (something like) an AST of the passed function. I don't think it works if the lambda contained any loops or recursion, though.
BTW: Can LINQ do that? I've only seen simple expressions in the examples. That should be possible using python, too.

Popular posts from this blog

CARDIAC: The Cardboard Computer

I am just so excited about this. CARDIAC. The Cardboard Computer. How cool is that? This piece of history is amazing and better than that: it is extremely accessible. This fantastic design was built in 1969 by David Hagelbarger at Bell Labs to explain what computers were to those who would otherwise have no exposure to them. Miraculously, the CARDIAC (CARDboard Interactive Aid to Computation) was able to actually function as a slow and rudimentary computer.  One of the most fascinating aspects of this gem is that at the time of its publication the scope it was able to demonstrate was actually useful in explaining what a computer was. Could you imagine trying to explain computers today with anything close to the CARDIAC? It had 100 memory locations and only ten instructions. The memory held signed 3-digit numbers (-999 through 999) and instructions could be encoded such that the first digit was the instruction and the second two digits were the address of memory to operate on

The Range of Content on Planet Python

I've gotten a number of requests lately to contribute only Python related material to the Planet Python feeds and to be honest these requests have both surprised and insulted me, but they've continued. I am pretty sure they've come from a very small number of people, but they have become consistent. This is probably because of my current habit of writing about NaNoWriMo every day and those who aren't interested not looking forward to having the rest of the month reading about my novel. Planet Python will be getting a feed of only relevant posts in the future, but I'm going to be honest: I am kind of upset about it. I don't care if anyone thinks it is unreasonable of me to be upset about it, because the truth is Planet Python means something to me. It was probably the first thing I did that I considered "being part of the community" when I submitted my meager RSS feed to be added some seven years ago. My blog and my name on the list of authors at Plan

Interrupting Coders Isn’t So Bad

Here’s a hot take: disrupting coders isn’t all that bad. Some disruptions are certainly bad but they usually aren’t. The coder community has overblown the impact. A disruption can be a good thing. How harmful disruption might be a symptom of other problems. There are different kinds of disruptions. They are caused by other coders on your team, managers and other non-coders, or meetings throughout the day. The easiest example to debunk is a question from a fellow developer. Imagine someone walks over to your desk or they ping you on Slack, because they have “one quick question.” Do you get annoyed at the interruption when you were in the middle of something important? You help out your teammate quickly and get back to work, trying to pick up where you left off. That’s a kind of interruption we complain about frequently, but I’m not convinced this is all that bad. You are being disrupted but your team, of which you are only one member of the whole unit, is working smoothly. You u