[Python-checkins] CVS: python/dist/src/Misc NEWS,1.113,1.114

[Jeremy Hylton]

Update of /cvsroot/python/python/dist/src/Misc
In directory usw-pr-cvs1:/tmp/cvs-serv19176/Misc

Modified Files:
	NEWS 
Log Message:
Add item about nested scopes.

Revise item about restriction on 'from ... import *'.  It was in the
wrong section and the section restriction was removed. 


Index: NEWS
===================================================================
RCS file: /cvsroot/python/python/dist/src/Misc/NEWS,v
retrieving revision 1.113
retrieving revision 1.114
diff -C2 -r1.113 -r1.114
*** NEWS	2001/02/01 20:00:40	1.113
--- NEWS	2001/02/01 20:38:45	1.114
***************
*** 4,7 ****
--- 4,40 ----
  Core language, builtins, and interpreter
  
+ - Scopes nest.  If a name is used in a function or class, but is not
+   local, the definition in the nearest enclosing function scope will
+   be used.  One consequence of this change is that lambda statements
+   could reference variables in the namespaces where the lambda is
+   defined.  In some unusual cases, this change will break code.
+ 
+   In all previous version of Python, names were resolved in exactly
+   three namespaces -- the local namespace, the global namespace, and
+   the builtin namespace.  According to this old defintion, if a
+   function A is defined within a function B, the names bound in B are
+   not visible in A.  The new rules make names bound in B visible in A,
+   unless A contains a name binding that hides the binding in B.
+ 
+   Section 4.1 of the reference manual describes the new scoping rules
+   in detail.  The test script in Lib/test/test_scope.py demonstrates
+   some of the effects of the change.
+ 
+   The new rules will cause existing code to break if it defines nested
+   functions where an outer function has local variables with the same
+   name as globals or builtins used by the inner function.  Example:
+ 
+     def munge(str):
+         def helper(x):
+             return str(x)
+         if type(str) != type(''):
+             str = helper(str)
+         return str.strip()
+ 
+   Under the old rules, the name str in helper() is bound to the
+   builtin function str().  Under the new rules, it will be bound to
+   the argument named str and an error will occur when helper() is
+   called.
+ 
  - repr(string) is easier to read, now using hex escapes instead of octal,
    and using \t, \n and \r instead of \011, \012 and \015 (respectively):
***************
*** 14,17 ****
--- 47,56 ----
    the func_code attribute is writable.
  
+ - The compiler will report a SyntaxError if "from ... import *" occurs
+   in a function or class scope.  The language reference has documented
+   that this case is illegal, but the compiler never checked for it.
+   The recent introduction of nested scope makes the meaning of this
+   form of name binding ambiguous.
+ 
  - Weak references (PEP 205) have been added.  This involves a few
    changes in the core, an extension module (_weakref), and a Python
***************
*** 60,69 ****
  
  Core language, builtins, and interpreter
- 
- - The compiler will report a SyntaxError if "from ... import *" occurs
-   in a function or class scope or if a name bound by the import
-   statement is declared global in the same scope.  The language
-   reference has also documented that these cases are illegal, but
-   they were not enforced.
  
  - There is a new Unicode companion to the PyObject_Str() API
--- 99,102 ----