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Problems I Have with Python

darkf.github.io

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Re: Problems I Have with Python

#31

Post by spookylukey »

orf wrote: post #15
Loic wrote: post #3

The one problem I have with Python and would like to solve, is to be able, from within a request rendering function/method of my web application (think Flask) to run something like: handle1 = call_webservice_1(args) handle2 = call_webservice_2(args) handle3 = call_webservice_3(args) (realres1, realres2, realres3) = wait_until_timeout(500, handle1, handle2, handle3) # here, I have my results in realresX or None if tim…

from asyncio import wait, gather, get_event_loop from aiohttp import web async my_handler(request): handle1 = call_webservice_1(args) handle2 = call_webservice_2(args) handle3 = call_webservice_3(args) await wait(gather(handle1, handle2, handle3), 500) return web.Response({'finished': True}) app = web.Application() app.router.add_route('GET', '/test/', my_handler) loop = asyncio.get_event_loop() server = loop.create_…

That's really helpful. Can you make an example which doesn't require making the my_handler function 'async'? For cases when you don't want to make an entire async stack, you just want to slot some async code into your existing code.

If the answer is "to get some async goodness, just use this easy code, plus rewrite your entire project to use a different framework and set of libraries", then we are only fooling ourselves.

Re: Problems I Have with Python

#32

Post by cybersol »

It's definitely not perfect, though ultimately most trade-offs in Python come down to readability. I once went down the rabbit hole (3 library iterations) of overloading operators to enable a very shell and pipe oriented syntax, only to later realize how much harder my 6-month old code was to read even for me. So I've come to appreciate Guido's experience for the trade-off between expressive power and readability.

For instance in the things you suggest, reduce used in its most straightforward manner is readable, but it can also be used to enable some of nastiest, most head scratching one liners. Lambda is useful for small things like callbacks, but readability should lead you to a real function with a descriptive name sooner rather than later.

Re: Problems I Have with Python

#33

Post by AnkhMorporkian »

spookylukey wrote: post #31
orf wrote: post #15

Earlier quoted context omitted.

from asyncio import wait, gather, get_event_loop from aiohttp import web async my_handler(request): handle1 = call_webservice_1(args) handle2 = call_webservice_2(args) handle3 = call_webservice_3(args) await wait(gather(handle1, handle2, handle3), 500) return web.Response({'finished': True}) app = web.Application() app.router.add_route('GET', '/test/', my_handler) loop = asyncio.get_event_loop() server = loop.create_…

That's really helpful. Can you make an example which doesn't require making the my_handler function 'async'? For cases when you don't want to make an entire async stack, you just want to slot some async code into your existing code. If the answer is "to get some async goodness, just use this easy code, plus rewrite your entire project to use a different framework and set of libraries", then we are only fooling oursel…

You need to use the asyncio (or equivalent) event loop if you want to use the asnycio module. loop.run_until_complete() is synchronous though, so you would simply call that and it will block the control flow despite that function being async. You can definitely mix it with legacy code.

I would recommend against it, but if you had an existing framework, you could just make the endpoints lambdas that are something like:

    app.route("/whatever", lambda: loop.run_until_complete(async_handler_function()))

Re: Problems I Have with Python

#34

Post by rushi_agrawal »

I realize that after reading the article, most people (including me, unfortunately) read the article as 'Problems WE have with Python'. Maybe a line by author at the top or bottom of the article, reiterating that it's the problem 'he' has with Python -- I know nobody would think such a second clarification would be necessary, but hey, we're humans! -- would help.

Re: Problems I Have with Python

#35

Post by ankitml »

It is hard to accept inputs from people who dont appreciate that any technical decision require understanding the tradeoffs. It is true that python is not perfect, but perfection was never a goal. Python has made some tradeoffs, just like every other technical system. Also, just like any other technical system people are working towards improving in a specific direction. They only way to change or evolve that direction is to be part of the community, understanding it, and then influencing it. Abusing the community, calling it silly is plain stupid. The author's goal is clearly not in influencing a change but self aggrandising and proving himself right.

Re: Problems I Have with Python

#36

Post by orf »

spookylukey wrote: post #31
orf wrote: post #15

Earlier quoted context omitted.

from asyncio import wait, gather, get_event_loop from aiohttp import web async my_handler(request): handle1 = call_webservice_1(args) handle2 = call_webservice_2(args) handle3 = call_webservice_3(args) await wait(gather(handle1, handle2, handle3), 500) return web.Response({'finished': True}) app = web.Application() app.router.add_route('GET', '/test/', my_handler) loop = asyncio.get_event_loop() server = loop.create_…

That's really helpful. Can you make an example which doesn't require making the my_handler function 'async'? For cases when you don't want to make an entire async stack, you just want to slot some async code into your existing code. If the answer is "to get some async goodness, just use this easy code, plus rewrite your entire project to use a different framework and set of libraries", then we are only fooling oursel…

Sure, you can make an async function and call `loop.run_until_complete` in your handler.

Re: Problems I Have with Python

#37

Post by lmm »

darkf wrote: post #21
lmm wrote: post #19

Python's semantics are unlikely to ever be fast and most Python users have already worked around its speed issues. asyncio is new; python3 porting is happening. It seems unfair to complain that no real improvements are being made and also complain that these new things are immature. reduce being pushed behind an import is stupid, but it's only one import. lambda is fine, if you're writing in functional style you're u…

>lambda is fine, if you're writing in functional style you're using expressions for everything anyway. No, I /really would/ like to be able to write: foo.on_click(lambda: x += 1) The language not supporting this (when most others do) is just silly.

That seems like an exceedingly error-prone thing to write. "x +=1" isn't a value and the unmanaged mutation will be surprising when it happens. On a Python implementation with parallelism (e.g. Jython) you could very easily end up losing updates - on CPython the GIL will probably mean your code accidentally doesn't exhibit that problem, but that doesn't seem a very desirable way to code.

Re: Problems I Have with Python

#38

Post by dev360 »

fleetfox wrote: post #25
Grue3 wrote: post #18

I like this list a lot. I also find myself raging at awful lambda and the lack of switch. No, it wouldn't make the language any less "pythonic" to make them useful.

IMHO switch is horrible construct i'd rather see ML style pattern matching

Pattern matching without TCO would leave me feeling deceived

Re: Problems I Have with Python

#39

Post by tacostakohashi »

The problem I have with Python is that for loops don't have their own scope, only methods.

Add that to the lack of variable declarations (even optional ones, a la my in perl, var in javascript), and it gets hard to work out what scope of any given variable actually is.

Surprising example:

  fns = []

  for n in [1,2,3,4]:
    def fn():
      print(n)
    fns.append(fn)

  for fn in fns:
    fn()

Re: Problems I Have with Python

#40

Post by gamesbrainiac »

I think there are many people out there who use python because its practical and useful to them, but they don't love it, and that is completely fine. Anything good is a compromise between different groups and Python is no exception to that rule. I think Python does a decent job at appeasing both functional zealots as well as objection oriented fanatics.
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