compat: adds a max function taking 'key' as keyword argument

3 files changed, 78 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 9343b55..272840a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -10,6 +10,7 @@ ChangeLog for logilab.common
       - added assertUnorderedIterableEquals
 	
     * umessage.date() return unparsage string as is instead of None
+    * compat: adds a max function taking 'key' as keyword argument
 2008-09-08  --  0.32.0
     * textutils: add the apply_unit fonction
     * testlib:
diff --git a/compat.py b/compat.py
index 7e98330..fc2b231 100644
--- a/compat.py
+++ b/compat.py
@@ -22,6 +22,8 @@ from __future__ import generators
 
 from warnings import warn
 
+import __builtin__
+
 from logilab.common.deprecation import class_renamed
 
 try:
@@ -188,6 +190,44 @@ except NameError:
         l2.reverse()
         return l2
 
+try: #
+    max = max
+    max(("ab","cde"),key=len)
+except TypeError:
+    def max( *args, **kargs):
+        if len(args) == 0:
+            raise TypeError("max expected at least 1 arguments, got 0")
+        key= kargs.pop("key", None)
+        #default implementation
+        if key is None:
+            return __builtin__.max(*args,**kargs)
+
+        for karg in kargs:
+            raise TypeError("unexpected keyword argument %s for function max") % karg
+
+        if len(args) == 1:
+            items = iter(args[0])
+        else:
+            items = iter(args)
+        
+        try:
+            best_item = items.next()
+            best_value = key(best_item)
+        except StopIteration:
+            raise ValueError("max() arg is an empty sequence")
+        
+        for item in items:
+            value = key(item)
+            if value > best_value:
+                best_item = item
+                best_value = value
+
+        return best_item
+
+
+
+
+
 # Python2.5 builtins
 try:
     any = any
diff --git a/test/unittest_compat.py b/test/unittest_compat.py
index b9c7cd0..eaa769b 100644
--- a/test/unittest_compat.py
+++ b/test/unittest_compat.py
@@ -9,11 +9,13 @@ import pprint
 class CompatTCMixIn:
     MODNAMES = {}
     BUILTINS = []
+    ALTERED_BUILTINS = {}
     
     def setUp(self):
         self.builtins_backup = {}
         self.modules_backup = {}
         self.remove_builtins()
+        self.alter_builtins()
         self.remove_modules()
     
     def tearDown(self):
@@ -36,6 +38,13 @@ class CompatTCMixIn:
                 self.builtins_backup[builtin] = func
                 delattr(__builtin__, builtin)
                 # setattr(__builtin__, 'builtin_%s' % builtin, func)
+    def alter_builtins(self):
+        for builtin, func in self.ALTERED_BUILTINS.iteritems():
+            old_func = getattr(__builtin__, builtin, None)
+            if func is not None:
+                self.builtins_backup[builtin] = old_func
+                setattr(__builtin__, builtin, func)
+                # setattr(__builtin__, 'builtin_%s' % builtin, func)
                 
     def remove_modules(self):
         for modname in self.MODNAMES:
@@ -147,9 +156,18 @@ class Py24CompatTC(CompatTCMixIn, TestCase):
 
 
 
+class _MaxFaker(object):
+    def __init__(self, func):
+        self.func = func
+    def fake(self,*args,**kargs):
+        if kargs:
+            raise TypeError("max() takes no keyword argument")
+        return self.func(*args)
+        
 
 class Py25CompatTC(CompatTCMixIn, TestCase):
     BUILTINS = ('any', 'all',)
+    ALTERED_BUILTINS = {'max': _MaxFaker(max).fake}
 
     def test_any(self):
         from logilab.common.compat import any
@@ -180,7 +198,25 @@ class Py25CompatTC(CompatTCMixIn, TestCase):
         self.assertEquals(all(irange), False)
         self.assertEquals(irange.next(), 1)
 
-
+    def test_max(self):
+        from logilab.common.compat import max
+    
+        # old apy
+        self.assertEquals(max("fdjkmhsgmdfhsg"),'s')
+        self.assertEquals(max(1,43,12,45,1337,34,2), 1337)
+        self.assertRaises(TypeError,max)
+        self.assertRaises(TypeError,max,1)
+        self.assertRaises(ValueError,max,[])
+        self.assertRaises(TypeError,max,bob=None)
+
+        # new apy
+        self.assertEquals(max("shorter","longer",key=len),"shorter")
+        self.assertEquals(max(((1,1),(2,3,5),(8,13,21)),key=len),(2,3,5))
+        self.assertEquals(max(((1,1),(42,),(2,3,5),(8,13,21)),key=max),(42,))
+        self.assertRaises(TypeError,max,key=None)
+        self.assertRaises(TypeError,max,1,key=len)
+        self.assertRaises(ValueError,max,[],key=max)
+        self.assertRaises(TypeError,max,"shorter","longer",key=len,kathy=None)
 
 if __name__ == '__main__':
     unittest_main()