bpo-13487: Use sys.modules.copy() in inspect.getmodule() for thread safety. (GH-18786)
`list(sys.modules.items())` was apparently not immune to "dictionary
changed size during iteration" errors.
Tested internally using an integration test that has run into this a couple of times in the past two years. With this patch applied, the test is no longer flaky.
diff --git a/Lib/inspect.py b/Lib/inspect.py
index bb82f96..125bd45 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -741,7 +741,7 @@
return sys.modules.get(modulesbyfile[file])
# Update the filename to module name cache and check yet again
# Copy sys.modules in order to cope with changes while iterating
- for modname, module in list(sys.modules.items()):
+ for modname, module in sys.modules.copy().items():
if ismodule(module) and hasattr(module, '__file__'):
f = module.__file__
if f == _filesbymodname.get(modname, None):
diff --git a/Misc/NEWS.d/next/Library/2020-03-04-16-10-59.bpo-13487.gqe4Fb.rst b/Misc/NEWS.d/next/Library/2020-03-04-16-10-59.bpo-13487.gqe4Fb.rst
new file mode 100644
index 0000000..5a1f02a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-03-04-16-10-59.bpo-13487.gqe4Fb.rst
@@ -0,0 +1,3 @@
+Avoid a possible *"RuntimeError: dictionary changed size during iteration"*
+from :func:`inspect.getmodule` when it tried to loop through
+:attr:`sys.modules`.