4 Other Language Changes

Here are all of the changes that Python 2.5 makes to the core Python language.

The min() and max() built-in functions gained a key keyword argument analogous to the key argument for sort(). This argument supplies a function that takes a single argument and is called for every value in the list; min()/max() will return the element with the smallest/largest return value from this function. For example, to find the longest string in a list, you can do:
```
L = ['medium', 'longest', 'short']
# Prints 'longest'
print max(L, key=len)		   
# Prints 'short', because lexicographically 'short' has the largest value
print max(L)
```
(Contributed by Steven Bethard and Raymond Hettinger.)
Two new built-in functions, any() and all(), evaluate whether an iterator contains any true or false values. any() returns True if any value returned by the iterator is true; otherwise it will return False. all() returns True only if all of the values returned by the iterator evaluate as being true.
The list of base classes in a class definition can now be empty. As an example, this is now legal:
```
class C():
    pass
```
(Implemented by Brett Cannon.)

4.1 Optimizations

When they were introduced in Python 2.4, the built-in set and frozenset types were built on top of Python's dictionary type. In 2.5 the internal data structure has been customized for implementing sets, and as a result sets will use a third less memory and are somewhat faster. (Implemented by Raymond Hettinger.)

The net result of the 2.5 optimizations is that Python 2.5 runs the pystone benchmark around XX% faster than Python 2.4.

See About this document... for information on suggesting changes.