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

Chris Angelico rosuav at gmail.com
Sun Oct 8 07:44:51 EDT 2017

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.


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