importlib sometimes fails to import a recently created module

[rjdymond]

BPO	23412
Nosy	@brettcannon, @ncoghlan, @ericsnowcurrently
Files	importerror.py

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2015-02-09.15:45:49.948>
created_at = <Date 2015-02-08.15:43:35.922>
labels = ['interpreter-core', 'type-bug', 'invalid']
title = 'importlib sometimes fails to import a recently created module'
updated_at = <Date 2015-02-09.15:45:49.947>
user = 'https://bugs.python.org/rjdymond'

bugs.python.org fields:

activity = <Date 2015-02-09.15:45:49.947>
actor = 'brett.cannon'
assignee = 'none'
closed = True
closed_date = <Date 2015-02-09.15:45:49.948>
closer = 'brett.cannon'
components = ['Interpreter Core']
creation = <Date 2015-02-08.15:43:35.922>
creator = 'rjdymond'
dependencies = []
files = ['38046']
hgrepos = []
issue_num = 23412
keywords = []
message_count = 3.0
messages = ['235557', '235559', '235617']
nosy_count = 5.0
nosy_names = ['brett.cannon', 'ncoghlan', 'SilentGhost', 'eric.snow', 'rjdymond']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue23412'
versions = ['Python 3.3', 'Python 3.4', 'Python 3.5']

[rjdymond]

importlib.import_module() sometimes fails to import a module that has just been written to the filesystem, aborting with an ImportError.

Example output when executing the attached file with Python 3.3 or 3.4:

Wrote tmpwbzb35.py
  Successfully imported tmpwbzb35
Wrote tmp34c6qs.py
Traceback (most recent call last):
  File "importerror.py", line 12, in <module>
    importlib.import_module(modname)
  File "/home/rjd/Python/Python3.3/lib/python3.3/importlib/__init__.py", line 88, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1577, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1558, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1522, in _find_and_load_unlocked
ImportError: No module named 'tmp34c6qs'

I have been unable to reproduce this behaviour with Python 2.7 or Python 3.2.

[SilentGhost]

Looks like some sort of race condition. Sleeping for a second before import_module seem to solve the problem.

[brettcannon]

Because stat results are cached for performance reasons, it's possible to write to the file system and then try to read/import from it before the modification time for the directory even picks up that there was a change. For this reason there is importlib.invalidate_caches(): https://docs.python.org/3/library/importlib.html#importlib.invalidate_caches .

I have opened http://bugs.python.org/issue23422 to track that the docs for importlib.import_module() point out invalidate_caches().