(original) (raw)

On Sun, Oct 8, 2017 at 7:02 PM, David Cournapeau <cournape@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.