Do not touch sys.path when site is imported and python was started with -S.
Original patch by Carl Meyer, review by Brett Cannon, small doc editions by
yours truly. Fixes #11591.
diff --git a/Doc/library/site.rst b/Doc/library/site.rst
index b77f3cf..4b7a234 100644
--- a/Doc/library/site.rst
+++ b/Doc/library/site.rst
@@ -13,7 +13,11 @@
.. index:: triple: module; search; path
-Importing this module will append site-specific paths to the module search path.
+Importing this module will append site-specific paths to the module search
+path, unless :option:`-S` was used. In that case, this module can be safely
+imported with no automatic modifications to the module search path. To
+explicitly trigger the usual site-specific additions, call the
+:func:`site.main` function.
.. index::
pair: site-python; directory
@@ -114,6 +118,13 @@
.. envvar:: PYTHONUSERBASE
+.. function:: main()
+
+ Adds all the standard site-specific directories to the module search
+ path. This function is called automatically when this module is imported,
+ unless the :program:`python` interpreter was started with the :option:`-S`
+ flag.
+
.. function:: addsitedir(sitedir, known_paths=None)
Adds a directory to sys.path and processes its pth files.
diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index d1f47eb..b5a9b32 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -239,7 +239,9 @@
.. cmdoption:: -S
Disable the import of the module :mod:`site` and the site-dependent
- manipulations of :data:`sys.path` that it entails.
+ manipulations of :data:`sys.path` that it entails. Also disable these
+ manipulations if :mod:`site` is explicitly imported later (call
+ :func:`site.main` if you want them to be triggered).
.. cmdoption:: -u
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index d86826c..7f05a84 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -128,3 +128,8 @@
* Stub
+
+.. Issue #11591: When :program:`python` was started with :option:`-S`,
+ ``import site`` will not add site-specific paths to the module search
+ paths. In previous versions, it did. See changeset for doc changes in
+ various files. Contributed by Carl Meyer with editions by Éric Araujo.
diff --git a/Lib/site.py b/Lib/site.py
index a2c0bec..fcfdbed 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -508,6 +508,11 @@
def main():
+ """Add standard site-specific directories to the module search path.
+
+ This function is called automatically when this module is imported,
+ unless the python interpreter was started with the -S flag.
+ """
global ENABLE_USER_SITE
abs_paths()
@@ -526,7 +531,10 @@
if ENABLE_USER_SITE:
execusercustomize()
-main()
+# Prevent edition of sys.path when python was started with -S and
+# site is imported later.
+if not sys.flags.no_site:
+ main()
def _script():
help = """\
diff --git a/Misc/NEWS b/Misc/NEWS
index e8a1926..363d5e9 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -81,12 +81,15 @@
Library
-------
+- Issue #11591: Prevent "import site" from modifying sys.path when python
+ was started with -S.
+
- Issue #11371: Mark getopt error messages as localizable. Patch by Filip
Gruszczyński.
- Issue #11333: Add __slots__ to collections ABCs.
-- Issue #11628: cmp_to_key generated class should use __slots__
+- Issue #11628: cmp_to_key generated class should use __slots__.
- Issue #5537: Fix time2isoz() and time2netscape() functions of
httplib.cookiejar for expiration year greater than 2038 on 32-bit systems.
diff --git a/Misc/python.man b/Misc/python.man
index 2d15d5d..53b77fc 100644
--- a/Misc/python.man
+++ b/Misc/python.man
@@ -169,7 +169,9 @@
.I site
and the site-dependent manipulations of
.I sys.path
-that it entails.
+that it entails. Also disable these manipulations if
+.I site
+is explicitly imported later.
.TP
.B \-u
Force the binary I/O layers of stdin, stdout and stderr to be unbuffered.