Clarify that the description of sys.path[0] is only valid upon program

start-up.

diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 76aaefd92508d6b0a342829f5fc221ec5b13ee37..4aa2d4a14ec81a0935d2d96ac290e0b2c5e4a4fd 100644 (file)
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -282,10 +282,11 @@ else:
 \begin{datadesc}{path}
 \indexiii{module}{search}{path}
   A list of strings that specifies the search path for modules.
-  Initialized from the environment variable \envvar{PYTHONPATH}, or an
+  Initialized from the environment variable \envvar{PYTHONPATH}, plus an
   installation-dependent default.
 
-  The first item of this list, \code{path[0]}, is the directory
+  As initialized upon program startup,
+  the first item of this list, \code{path[0]}, is the directory
   containing the script that was used to invoke the Python
   interpreter.  If the script directory is not available (e.g.  if the
   interpreter is invoked interactively or if the script is read from
@@ -293,6 +294,8 @@ else:
   Python to search modules in the current directory first.  Notice
   that the script directory is inserted \emph{before} the entries
   inserted as a result of \envvar{PYTHONPATH}.
+
+  A program is free to modify this list for its own purposes.
 \end{datadesc}
 
 \begin{datadesc}{platform}