Adds comment to explain the use of sys.base_prefix

1 files changed, 11 insertions, 3 deletions

diff --git a/astroid/modutils.py b/astroid/modutils.py
index 87d58b4f..2cab500e 100644
--- a/astroid/modutils.py
+++ b/astroid/modutils.py
@@ -90,6 +90,17 @@ if os.name == "nt":
             pass
 
 if platform.python_implementation() == "PyPy":
+    # The get_python_lib(standard_lib=True) function does not give valid
+    # result with pypy in a virtualenv.
+    # In a virtual environment, with CPython implementation the call to this function returns a path toward
+    # the binary (its libraries) which has been used to create the virtual environment.
+    # Not with pypy implementation.
+    # The only way to retrieve such information is to use the sys.base_prefix hint.
+    # It's worth noticing that under CPython implementation the return values of 
+    # get_python_lib(standard_lib=True) and get_python_lib(santdard_lib=True, prefix=sys.base_prefix)
+    # are the same.
+    # In the lines above, We could have replace the call to get_python_lib(standard=True)
+    # with the one using prefix=sys.base_prefix but we prefer modifying only what deals with pypy.
     STD_LIB_DIRS.add(get_python_lib(standard_lib=True, prefix=sys.base_prefix))
     _root = os.path.join(sys.prefix, "lib_pypy")
     STD_LIB_DIRS.add(_root)
@@ -535,9 +546,6 @@ def is_standard_module(modname, std_path=None):
             return False
     if std_path is None:
         std_path = STD_LIB_DIRS
-    if modname == "hashlib":
-        print(f"Module {modname} is located in {filename}")
-        print(f"STD_LIB_DIRS are {STD_LIB_DIRS}")
     for path in std_path:
         if filename.startswith(_cache_normalize_path(path)):
             return True