gh-118761: Improve import time of subprocess (GH-129427)

hukkin · web-flow · commit 49f24650e454 · 2025-01-29T08:31:13.000-08:00
* subprocess: lazy import signal and locale to improve module import time
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
@@ -43,10 +43,8 @@
 import builtins
 import errno
 import io
-import locale
 import os
 import time
-import signal
 import sys
 import threading
 import warnings
@@ -144,6 +142,8 @@ def __init__(self, returncode, cmd, output=None, stderr=None):
 
     def __str__(self):
         if self.returncode and self.returncode < 0:
+            # Lazy import to improve module import time
+            import signal
             try:
                 return "Command '%s' died with %r." % (
                         self.cmd, signal.Signals(-self.returncode))
@@ -381,6 +381,8 @@ def _text_encoding():
     if sys.flags.utf8_mode:
         return "utf-8"
     else:
+        # Lazy import to improve module import time
+        import locale
         return locale.getencoding()
 
 
@@ -1664,6 +1666,9 @@ def send_signal(self, sig):
             # Don't signal a process that we know has already died.
             if self.returncode is not None:
                 return
+
+            # Lazy import to improve module import time
+            import signal
             if sig == signal.SIGTERM:
                 self.terminate()
             elif sig == signal.CTRL_C_EVENT:
@@ -1765,6 +1770,9 @@ def _posix_spawn(self, args, executable, env, restore_signals, close_fds,
             """Execute program using os.posix_spawn()."""
             kwargs = {}
             if restore_signals:
+                # Lazy import to improve module import time
+                import signal
+
                 # See _Py_RestoreSignals() in Python/pylifecycle.c
                 sigset = []
                 for signame in ('SIGPIPE', 'SIGXFZ', 'SIGXFSZ'):
@@ -2214,9 +2222,13 @@ def send_signal(self, sig):
         def terminate(self):
             """Terminate the process with SIGTERM
             """
+            # Lazy import to improve module import time
+            import signal
             self.send_signal(signal.SIGTERM)
 
         def kill(self):
             """Kill the process with SIGKILL
             """
+            # Lazy import to improve module import time
+            import signal
             self.send_signal(signal.SIGKILL)
diff --git a/Misc/NEWS.d/next/Library/2025-01-29-10-53-32.gh-issue-118761.i8wjpV.rst b/Misc/NEWS.d/next/Library/2025-01-29-10-53-32.gh-issue-118761.i8wjpV.rst
@@ -0,0 +1,2 @@
+Improve import time of :mod:`subprocess` by lazy importing ``locale`` and
+``signal``. Patch by Taneli Hukkinen.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Improve import time of :mod:`subprocess` by lazy importing ``locale`` and
	`2`	+``signal``. Patch by Taneli Hukkinen.