How to wrap every method of a class?

An elegant way to do it is described in Michael Foord's Voidspace blog in an entry about what metaclasses are and how to use them in the section titled A Method Decorating Metaclass. Simplifying it slightly and applying it to your situation resulted in this:

from functools import wraps
from types import FunctionType

def wrapper(method):
    @wraps(method)
    def wrapped(*args, **kwargs):
    #   ... <do something to/with "method" or the result of calling it>
    return wrapped

class MetaClass(type):
    def __new__(meta, classname, bases, classDict):
        newClassDict = {}
        for attributeName, attribute in classDict.items():
            if isinstance(attribute, FunctionType):
                # replace it with a wrapped version
                attribute = wrapper(attribute)
            newClassDict[attributeName] = attribute
        return type.__new__(meta, classname, bases, newClassDict)

class MyClass(object):
    __metaclass__ = MetaClass  # wrap all the methods
    def method1(self, ...):
        # ...etc ...

In Python, function/method decorators are just function wrappers plus some syntactic sugar to make using them easy (and prettier).

Python 3 Compatibility Update

The previous code uses Python 2.x metaclass syntax which would need to be translated in order to be used in Python 3.x, however it would then no longer work in the previous version. This means it would need to use:

class MyClass(metaclass=MetaClass)  # apply method-wrapping metaclass
    ...

instead of:

class MyClass(object):
    __metaclass__ = MetaClass  # wrap all the methods
    ...

If desired, it's possible to write code which is compatible with both Python 2.x and 3.x, but doing so requires using a slightly more complicated technique which dynamically creates a new base class that inherits the desired metaclass, thereby avoiding errors due to the syntax differences between the two versions of Python. This is basically what Benjamin Peterson's six module's with_metaclass() function does.

from types import FunctionType
from functools import wraps

def wrapper(method):
    @wraps(method)
    def wrapped(*args, **kwargs):
        print('{!r} executing'.format(method.__name__))
        return method(*args, **kwargs)
    return wrapped


class MetaClass(type):
    def __new__(meta, classname, bases, classDict):
        newClassDict = {}
        for attributeName, attribute in classDict.items():
            if isinstance(attribute, FunctionType):
                # replace it with a wrapped version
                attribute = wrapper(attribute)
            newClassDict[attributeName] = attribute
        return type.__new__(meta, classname, bases, newClassDict)


def with_metaclass(meta):
    """ Create an empty class with the supplied bases and metaclass. """
    return type.__new__(meta, "TempBaseClass", (object,), {})


if __name__ == '__main__':

    # Inherit metaclass from a dynamically-created base class.
    class MyClass(with_metaclass(MetaClass)):
        @staticmethod
        def a_static_method():
            pass

        @classmethod
        def a_class_method(cls):
            pass

        def a_method(self):
            pass

    instance = MyClass()
    instance.a_static_method()  # Not decorated.
    instance.a_class_method()   # Not decorated.
    instance.a_method()         # -> 'a_method' executing

You mean programatically set a wrapper to methods of a class?? Well, this is probably a really bad practice, but here's how you may do it:

def wrap_methods( cls, wrapper ):
    for key, value in cls.__dict__.items( ):
        if hasattr( value, '__call__' ):
            setattr( cls, key, wrapper( value ) )

If you have class, for example

class Test( ):
    def fire( self ):
        return True
    def fire2( self ):
        return True

and a wrapper

def wrapper( fn ):
    def result( *args, **kwargs ):
        print 'TEST'
        return fn( *args, **kwargs )
    return result

then calling

wrap_methods( Test, wrapper )

will apply wrapper to all methods defined in class Test. Use with caution! Actually, don't use it at all!