$ cat test.py 
#!/usr/bin/python
def decor(f):
    def wrapped(x):
         return f(x)+x
    return wrapped
def funct(x):
    return x**2
print funct(2)
@decor
def funct(x):
    return x**2
print funct(2)
$ ./test.py
4
6

def wrapped(x, ned_decor):
         return f(x)+x if ned_decor else f(x)

def a():
    pass
@smwdec
def b():
    a()

def decor(f):
    def wrapped(x):
         return f(x)+x
    return wrapped
 
def funct(x):
    return x**2
 
decorated_funct = decor(funct)
print funct(2), decorated_funct(2)