bpo-43423 Fix IndexError in subprocess _communicate function (GH-24777)
Check to make sure stdout and stderr are not empty before selecting an item from them in Windows subprocess._communicate.
Co-authored-by: Gregory P. Smith <greg@krypto.org>
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index e4ca5f5..d375514 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -1535,10 +1535,8 @@ def _communicate(self, input, endtime, orig_timeout):
self.stderr.close()
# All data exchanged. Translate lists into strings.
- if stdout is not None:
- stdout = stdout[0]
- if stderr is not None:
- stderr = stderr[0]
+ stdout = stdout[0] if stdout else None
+ stderr = stderr[0] if stderr else None
return (stdout, stderr)
diff --git a/Misc/NEWS.d/next/Library/2021-03-11-15-44-18.bpo-43423.rRomRD.rst b/Misc/NEWS.d/next/Library/2021-03-11-15-44-18.bpo-43423.rRomRD.rst
new file mode 100644
index 0000000..290d7fb
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-03-11-15-44-18.bpo-43423.rRomRD.rst
@@ -0,0 +1,2 @@
+:func:`subprocess.communicate` no longer raises an IndexError when there is an
+empty stdout or stderr IO buffer during a timeout on Windows.