ANNOUNCE: 'goto' for Python

[Daniel Yoo]

Michael Hudson <mwh at python.net> wrote:
: Camilo Olarte <colarte at telesat.com.co> writes:

:> >> Entrian Solutions is pleased to announce version 1.0 of the 'goto'
:> >> module.
:> >>
:> >> This adds the 'goto' and 'comefrom' keywords to Python 2.3, adding
:> >> flexibility to Python's control flow mechanisms and allowing Python
:> >> programmers to use many common control flow idioms that were previously
:> >> denied to them.
:> 
:> >>>>>>   What is the day today ? Oh yes the first of April !    <<<<<<
:> 
:> OOUCH ! I Almost believe it!

: There's nothing to believe: it works!


Hello,


It doesn't work from the interactive interpreter, though:

###
>>> from goto import goto, label
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python2.3/site-packages/goto.py", line 255, in _trace
    _addToCaches(filename)
  File "/usr/local/lib/python2.3/site-packages/goto.py", line 229, in _addToCaches
    for tokenType, tokenString, (startRow, startCol), (endRow, endCol), line \
IOError: [Errno 2] No such file or directory: '<stdin>'
###


I haven't looked at the code closely enough to understand exactly how
to fix this.  But in the meantime, here's a patch to at least give an
error message when one tries to use it interactively:



--- goto.py	Tue Mar 30 12:24:28 2004
+++ goto-fixed.py	Thu Apr  1 13:37:10 2004
@@ -208,6 +208,15 @@
 # Source filenames -> comefrom label names -> line numbers of those comefroms.
 _comefromNameCache = {}
 
+
+def _openModuleFilename(moduleFilename):
+    """Opens up the file named by moduleFilename.  In the special case where
+    the file is <stdin>, we raise an IOError."""
+    if moduleFilename == '<stdin>':
+        raise IOError, "module cannot be used on sys.stdin."
+    return open(moduleFilename, 'r')    
+
+
 def _addToCaches(moduleFilename):
     """Finds the labels and gotos in a module and adds them to the caches."""
 
@@ -227,7 +236,7 @@
     # Tokenize the module; 'window' is the last two (type, string) pairs.
     window = [(None, ''), (None, '')]
     for tokenType, tokenString, (startRow, startCol), (endRow, endCol), line \
-            in tokenize.generate_tokens(open(moduleFilename, 'r').readline):
+            in tokenize.generate_tokens(_openModuleFilename(moduleFilename).readline):
         # Plain goto: "goto .x"
         if window == plainGotoPattern:
             _plainGotoCache[moduleFilename][startRow] = tokenString



Hope this helps!