[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

Ok, the most important changes have been merged. Thanks everyone who helped on 
this large project! See also my summary email on python-dev:
https://mail.python.org/archives/list/python-...@python.org/thread/I3OQTA3F66NQUN7CH2NHC5XZTO24QCIK/

--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset cd27af70d58161c59072e27a10e0e63dcbf0bccb by Victor Stinner in 
branch 'master':
bpo-41718: Update runpy startup time What's New (GH-24998)
https://github.com/python/cpython/commit/cd27af70d58161c59072e27a10e0e63dcbf0bccb


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


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pull_request: https://github.com/python/cpython/pull/24998

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset bd9154a495434464283f74b660160f89930cd791 by Victor Stinner in 
branch 'master':
bpo-41718: runpy now imports pkgutil in functions (GH-24996)
https://github.com/python/cpython/commit/bd9154a495434464283f74b660160f89930cd791


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


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pull_request: https://github.com/python/cpython/pull/24996

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset d72e8d487553c103bf2742e229f8266b515fd951 by Victor Stinner in 
branch 'master':
bpo-41718: subprocess imports grp and pwd on demand (GH-24987)
https://github.com/python/cpython/commit/d72e8d487553c103bf2742e229f8266b515fd951


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

len(sys.modules) of msg376374 test_sys_modules:

* Python 3.6: 184
* Python 3.7: 183
* Python 3.8: 221
* Python 3.9: 233
* master: 131

The master branch imports 102 less modules than Python 3.9 (233 => 131)! Almost 
the half.

asyncio, logging, multiprocessing, etc. are no longer always imported by 
default.

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset 9feae41c4f04ca27fd2c865807a5caeb50bf4fc4 by Victor Stinner in 
branch 'master':
bpo-41718: libregrtest avoids importing datetime (GH-24985)
https://github.com/python/cpython/commit/9feae41c4f04ca27fd2c865807a5caeb50bf4fc4


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
pull_requests: +23747
pull_request: https://github.com/python/cpython/pull/24987

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
pull_requests: +23745
pull_request: https://github.com/python/cpython/pull/24985

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset 30793e81bd90f3346e962435d49073bc588f067c by Victor Stinner in 
branch 'master':
bpo-41718: Disable support.testresult XML output by default (GH-24982)
https://github.com/python/cpython/commit/30793e81bd90f3346e962435d49073bc588f067c


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset 0473fb222956063814b6beb5fd401f9eeaa8a56a by Victor Stinner in 
branch 'master':
bpo-41718: libregrtest runtest avoids import_helper (GH-24983)
https://github.com/python/cpython/commit/0473fb222956063814b6beb5fd401f9eeaa8a56a


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
pull_requests: +23743
pull_request: https://github.com/python/cpython/pull/24983

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
pull_requests: +23742
pull_request: https://github.com/python/cpython/pull/24982

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset 10417dd15f135c179cf4234d1abe506915d802ff by Victor Stinner in 
branch 'master':
bpo-41718: Reduce libregrtest runtest imports (GH-24980)
https://github.com/python/cpython/commit/10417dd15f135c179cf4234d1abe506915d802ff


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
pull_requests: +23741
pull_request: https://github.com/python/cpython/pull/24981

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
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pull_request: https://github.com/python/cpython/pull/24980

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:


New changeset 532e063fc2bf9e6e80550670ddc5dc5d2b1d2450 by Victor Stinner in 
branch 'master':
bpo-41718: regrtest saved_test_environment avoids imports (GH-24934)
https://github.com/python/cpython/commit/532e063fc2bf9e6e80550670ddc5dc5d2b1d2450


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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

Serhiy: "You could save/restore this data only when corresponded modules was 
imported, like it was done in clear_caches() in refleak.py."

That's a very good idea! I implemented it in PR 24934. But I modified runtest() 
to use *two* saved_test_environment instance. One before the test module is 
imported, one after. The one before is needed to check if the import itself has 
side effect, for example if the module body has side effect. The second is to 
check if running tests has side effect. The second one is more likely to have 
modules imported. The first one may miss some bugs, but IMO it's an acceptable 
trade-off.

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


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pull_request: https://github.com/python/cpython/pull/24934

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[issue41718] test.regrtest has way too many imports

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

>
> Yes, but they should be imported after running the test. Note that the
> default value in the example was changed from None to set().

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

> You could save/restore this data only when corresponded modules was imported, 
> like it was done in clear_caches() in refleak.py.

It was my first idea, but some large modules like multiprocessing and asyncio 
are only imported by tested when the test file is imported, whereas 
save_environment() is called (__enter__) before the import in 
libregrtest.runtest.

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[issue41718] test.regrtest has way too many imports

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

You could save/restore this data only when corresponded modules was imported, 
like it was done in clear_caches() in refleak.py. For example:

# Same for Process objects
def get_multiprocessing_process__dangling(self):
multiprocessing_process = sys.modules.get('multiprocessing.process')
if not multiprocessing_process:
return set()
# Unjoined process objects can survive after process exits
multiprocessing_process._cleanup()
# This copies the weakrefs without making any strong reference
return multiprocessing_process._dangling.copy()
def restore_multiprocessing_process__dangling(self, saved):
multiprocessing_process = sys.modules.get('multiprocessing.process')
if not multiprocessing_process:
return
multiprocessing_process._dangling.clear()
multiprocessing_process._dangling.update(saved)

--
nosy: +serhiy.storchaka

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[issue41718] test.regrtest has way too many imports

[Terry J. Reedy]

Terry J. Reedy  added the comment:

On Windows with current master, the baseline for running anything with 1 import 
(">>>  import sys; len(sys.modules)") is 35 imported modules.  Adding "import 
unittest" increases this to 80.  What slightly puzzles me is that running 
---
import unittest
import sys

class Tests(unittest.TestCase):
def test_bug(self):
print("len(sys.modules):", len(sys.modules))

if __name__ == "__main__":
unittest.main()
---
increases the number to 90.  Perhaps unittest has delayed imports.

The current startup number for IDLE is 162, which can result in a cold startup 
of several seconds.  I am thinking of trying to reduce this by delaying imports 
of modules that are not immediately used and might never be used.

For tests, I gather that side-effect issues are more important than startup 
time.

--
nosy: +terry.reedy

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
nosy: +pablogsal, zach.ware

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

In general, it's nice to have the following 4 checks:

* multiprocessing.process._dangling
* asyncio.events._event_loop_policy
* urllib.requests._url_tempfiles
* urllib.requests._opener

The problem is that because of these checks, **any** unit test file of the 424 
Python test files import asyncio, multiprocessing and urllib. As a result, 
**any** unit test starts with around 233 imported modules. We are far from an 
"unit" test, since many modules have side effects.

I wrote PR 22089 to remove these checks. "import test.libregrtest" is reduces 
from 233 to only 149 imports (on Linux), which is way better.

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

With PR 22089, test_sys_modules.py of msg376374 imports 152 imports rather than 
233. It's better than Python 2.7 which imports 170 modules!

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

Change by STINNER Victor :


--
keywords: +patch
pull_requests: +21175
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/22089

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

STINNER Victor  added the comment:

If I hack test.libregrtest.runtest to not import test.libregrtest.save_env, 
test_sys_modules imports only 148 instead of 233 modules.

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[issue41718] test.regrtest has way too many imports

[STINNER Victor]

New submission from STINNER Victor :

Follow-up of bpo-40275.

While investigating a crash on AIX (bpo-40068), I noticed that test_threading 
crashed because the test imports the logging module, and the logging has a bug 
on AIX on fork. I created an issue to reduce the number of imports made by 
"import test.support":

https://bugs.python.org/issue40275
I would prefer to better isolate tests: test_threading should only test the 
threading module, not the logging module.

Thanks to the hard work of Hai Shi, "import test.support" now imports only 37 
modules instead of 171! He split the 3200 lines of Lib/test/support/__init__.py 
into new helper submodules: bytecode, import, threading, socket, etc. For 
example, TESTFN now comes from test.support.os_helper.
Sadly, test.regrtest.save_env still imports asyncio and multiprocessing, and so 
in practice, running any test using "python -m test (...)" still imports around 
233 modules :-(

I measured the number of imports done in practice using the following file, 
Lib/test/test_sys_modules.py:

import unittest
from test import support
import sys

class Tests(unittest.TestCase):
def test_bug(self):
modules = sorted(sys.modules)
print("sys.modules:")
print("")
import pprint
pprint.pprint(modules)
print("")
print("len(sys.modules):", len(modules))

def test_main():
support.run_unittest(Tests)

if __name__ == "__main__":
test_main()


master:

* ./python -m test test_sys_modules: 233 modules (multiprocessing, asyncio, 
etc.)
* ./python Lib/test/test_sys_modules.py: 95 modules

3.9:

* ./python -m test test_sys_modules: 232
* ./python Lib/test/test_sys_modules.py: 117

3.5:

* ./python -m test test_sys_modules: 167
* ./python Lib/test/test_sys_modules.py: 151

2.7:

* ./python -m test test_sys_modules: 170
* ./python Lib/test/test_sys_modules.py: 122

--
components: Tests
messages: 376374
nosy: shihai1991, vstinner
priority: normal
severity: normal
status: open
title: test.regrtest has way too many imports
versions: Python 3.10

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