[Zope3-checkins] CVS: Zope3/src/datetime - _datetime.py:1.6 doc.txt:1.4

[Tim Peters]

Update of /cvs-repository/Zope3/src/datetime
In directory cvs.zope.org:/tmp/cvs-serv302/src/datetime

Modified Files:
	_datetime.py doc.txt 
Log Message:
datetimetz.astimezone():  don't call utcoffset() if the new timezone is
None; this sidesteps at least one "unbounded recursion surprise".  Admit
to the None case in the docs.


=== Zope3/src/datetime/_datetime.py 1.5 => 1.6 ===
--- Zope3/src/datetime/_datetime.py:1.5	Thu Dec 26 19:15:49 2002
+++ Zope3/src/datetime/_datetime.py	Fri Dec 27 16:34:51 2002
@@ -1614,14 +1614,16 @@
 
     def astimezone(self, tz):
         _check_tzinfo_arg(tz)
-        offset = self.utcoffset()
-        if offset is not None and tz is not None:
-            newoffset = tz.utcoffset(self)
-            if newoffset is not None:
-                if not isinstance(newoffset, timedelta):
-                    newoffset = timedelta(minutes=newoffset)
-                diff = offset - newoffset
-                self -= diff # this can overflow; can't be helped
+        # Don't call utcoffset unless it's necessary.
+        if tz is not None:
+            offset = self.utcoffset()
+            if offset is not None:
+                newoffset = tz.utcoffset(self)
+                if newoffset is not None:
+                    if not isinstance(newoffset, timedelta):
+                        newoffset = timedelta(minutes=newoffset)
+                    diff = offset - newoffset
+                    self -= diff # this can overflow; can't be helped
         return self.replace(tzinfo=tz)
 
     def isoformat(self, sep='T'):


=== Zope3/src/datetime/doc.txt 1.3 => 1.4 ===
--- Zope3/src/datetime/doc.txt:1.3	Thu Dec 26 19:15:49 2002
+++ Zope3/src/datetime/doc.txt	Fri Dec 27 16:34:51 2002
@@ -624,7 +624,7 @@
 
   - astimezone(tz)
     Return a datetimetz with the same date and time fields, and with
-    tzinfo=tz.  tz must be an instance of a tzinfo subclass.
+    tzinfo=tz.  tz must be None or an instance of a tzinfo subclass.
 
   - timetuple()
     Return a 9-element tuple of the form returned by time.localtime().
@@ -1131,9 +1131,9 @@
     tzinfo=None to remove a datetimetz's tzinfo member.
 
   - astimezone(tz)
-    Return a datetimetz with new tzinfo member.  tz must be an instance
-    of a tzinfo subclass.  If self is naive, or if tz.utcoffset(self)
-    returns None, self.astimezone(tz) is equivalent to
+    Return a datetimetz with new tzinfo member.  tz must be None or an
+    instance of a tzinfo subclass.  If tz is None, self is naive, or
+    tz.utcoffset(self) returns None, self.astimezone(tz) is equivalent to
     self.replace(tzinfo=tz):  a new timezone object is attached without
     any conversion of date or time fields.  If self is aware and
     tz.utcoffset(self) does not return None, the date and time fields