bpo-29877: compileall: import ProcessPoolExecutor only when needed (GH-4856)
Importing ProcessPoolExecutor may hang or cause an error when the import
accesses urandom on a low resource platform
https://bugs.python.org/issue29877
diff --git a/Lib/compileall.py b/Lib/compileall.py
index 7be23a6..aa65c6b 100644
--- a/Lib/compileall.py
+++ b/Lib/compileall.py
@@ -16,10 +16,6 @@
import py_compile
import struct
-try:
- from concurrent.futures import ProcessPoolExecutor
-except ImportError:
- ProcessPoolExecutor = None
from functools import partial
__all__ = ["compile_dir","compile_file","compile_path"]
@@ -70,9 +66,17 @@
workers: maximum number of parallel workers
invalidation_mode: how the up-to-dateness of the pyc will be checked
"""
- if workers is not None and workers < 0:
- raise ValueError('workers must be greater or equal to 0')
-
+ ProcessPoolExecutor = None
+ if workers is not None:
+ if workers < 0:
+ raise ValueError('workers must be greater or equal to 0')
+ elif workers != 1:
+ try:
+ # Only import when needed, as low resource platforms may
+ # fail to import it
+ from concurrent.futures import ProcessPoolExecutor
+ except ImportError:
+ workers = 1
files = _walk_dir(dir, quiet=quiet, maxlevels=maxlevels,
ddir=ddir)
success = True