Personally,

I am -1 on the name - I think '-X importtrace' or similar would be better I think.


I am +100 on the functionality - Unless you put in log messages, tracking imports is complex - so something like this I can see being very useful.


I know I don't make the decisions, but it seems if this really is only a couple of lines, and all the test cases pass this (or something very similar) should be a considered for 3.12.


Thank you Noah,




------ Original Message ------
From: "Noah Kim" <noahbkim@gmail.com>
To: python-ideas@python.org
Sent: Saturday, 11 Feb, 23 At 00:07
Subject: [Python-ideas] Proposal: -X importcache to supplement -X importtime for loaded modules

All,

I'm writing to propose an adjacent interpreter flag to `-X importtime`: `-X importcache` (open to alternative naming).

While `-X importtime` is incredibly useful for analyzing module import times, by design, it doesn't log anything if an imported module has already been loaded. `-X importcache` would provide additional output for every module that's already been loaded:

```
>>> import uuid
import time: cached | cached | _io
import time: cached | cached | _io
import time: cached | cached | os
import time: cached | cached | sys
import time: cached | cached | enum
import time: cached | cached | _io
import time: cached | cached | _io
import time: cached | cached | collections
import time: cached | cached | os
import time: cached | cached | re
import time: cached | cached | sys
import time: cached | cached | functools
import time: cached | cached | itertools
import time: 151 | 151 | _wmi
import time: 18290 | 18440 | platform
import time: 372 | 372 | _uuid
import time: 10955 | 29766 | uuid
```

In codebases with convoluted/poorly managed import graphs (and consequently, workloads that suffer from long import times), the ability to record all paths to an expensive dependency--not just the first-imported--can help expedite refactoring (and help scale identification of this type of issue). More generally, this flag would provide a more efficient path to tracking runtime dependencies.

As a proof of concept, I was able to hack this functionality into `-X importtime` by adding a couple lines to `import_ensure_initialized` in `Python/import.c` (hence the output above). A separate flag is probably desirable to preserve backwards compatibility.

Looking forward to your feedback,
Noah


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