[Python-Dev] Investigating time for `import requests`

[Koos Zevenhoven]

On Sun, Oct 8, 2017 at 2:44 PM, Chris Angelico <rosuav at gmail.com> wrote:

> On Sun, Oct 8, 2017 at 7:02 PM, David Cournapeau <cournape at gmail.com>
> wrote:
> > It is certainly true that for a CLI tool that actually makes any network
> > I/O, especially SSL, import times will quickly be negligible. It becomes
> > tricky for complex tools, because of error management. For example, a
> common
> > pattern I have used in the past is to have a high level "catch all
> > exceptions" function that dispatch the CLI command:
> >
> > try:
> >     main_function(...)
> > except ErrorKind1:
> >     ....
> > except requests.exceptions.SSLError:
> >     # gives complete message about options when receiving SSL errors,
> e.g.
> > invalid certificate
> >
> > This pattern requires importing requests every time the command is run,
> even
> > if no network IO is actually done. For complex CLI tools, maybe most
> command
> > don't use network IO (the tool in question was a complete packages
> manager),
> > but you pay ~100 ms because of requests import for every command. It is
> > particularly visible because commands latency starts to be felt around
> > 100-150 ms, and while you can do a lot in python in 100-150 ms, you
> can't do
> > much in 0-50 ms.
>
> This would be a perfect use-case for lazy importing, then. You'd pay
> the price of the import only if you get an error that isn't caught by
> one of the preceding except blocks.
>


​I suppose it might be convenient to be able to do something like:

with autoimport:
    try:
        main_function(...)
   ​ except ErrorKind1:
        ...
    except requests.exceptions.SLLError:
        ...


The easiest workaround at the moment is still pretty clumsy:

def import_SLLError():
    from requests.exceptions import SLLError
    return SLLError

...


    except import_SLLError():


But what happens if that gives you an ImportError?

––Koos


-- 
+ Koos Zevenhoven + http://twitter.com/k7hoven +
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20171008/c4d8fc88/attachment.html>