Bug #1462152: file() now checks more thoroughly for invalid mode

strings and removes a possible "U" before passing the mode to the
C library function.

1 files changed, 7 insertions, 1 deletions

diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex
index ff81faa..7cfdfbb 100644
--- a/Doc/lib/libfuncs.tex
+++ b/Doc/lib/libfuncs.tex
@@ -418,7 +418,7 @@ class C:
   that differentiate between binary and text files (else it is
   ignored).  If the file cannot be opened, \exception{IOError} is
   raised.
-
+  
   In addition to the standard \cfunction{fopen()} values \var{mode}
   may be \code{'U'} or \code{'rU'}. If Python is built with universal
   newline support (the default) the file is opened as a text file, but
@@ -434,6 +434,9 @@ class C:
   have yet been seen), \code{'\e n'}, \code{'\e r'}, \code{'\e r\e n'},
   or a tuple containing all the newline types seen.
 
+  Python enforces that the mode, after stripping \code{'U'}, begins with
+  \code{'r'}, \code{'w'} or \code{'a'}.
+
   If \var{mode} is omitted, it defaults to \code{'r'}.  When opening a
   binary file, you should append \code{'b'} to the \var{mode} value
   for improved portability.  (It's useful even on systems which don't
@@ -456,6 +459,9 @@ class C:
     determine whether this is the case.}
 
   \versionadded{2.2}
+
+  \versionchanged[Restriction on first letter of mode string
+                  introduced]{2.5}
 \end{funcdesc}
 
 \begin{funcdesc}{filter}{function, list}