Question

I have a python hash that contains a mapping of function name to function. I want to modify each hash entry to call the associated function BUT then to also call a final custom function. It’s to act somewhat like an exit hook.

def original():
    print "original work"

becomes

def replacement():
    original()
    print "notify somebody..."

My issue is I think I’m getting my scoping etc., wrong as the output of the following code is not as expected. Maybe if I could ask is there a better way to do this? I want to stick with modifying the original cb has as it third party code and less places I change the better.

#!/usr/bin/python 

def a():
    print "a"

def b():
    print "b"

def c():
    print "c"


orig_fxn_cb = dict()

" basic name to function callback hash "
orig_fxn_cb['a'] = a
orig_fxn_cb['b'] = b
orig_fxn_cb['c'] = c

" for each call back routine in the hash append a final action to it "
def appendFxn(fxn_cb):
    appended_fxn_cb_new = dict()
    for i in orig_fxn_cb.keys():
        cb = fxn_cb[i]
        def fxn_tail():
            cb()
            print cb.__name__, "tail" 

        appended_fxn_cb_new[i] = fxn_tail
        appended_fxn_cb_new[i]()
    return appended_fxn_cb_new

" make up a modified callback hash "
xxx = appendFxn(orig_fxn_cb)
print xxx

for i in xxx:
    print xxx[i]()

Answer 1

Are you after:

from functools import wraps

def notifier(f):
    @wraps(f)
    def wrapped(*args, **kwargs)
        res = f(*args, **kwargs)
        print "notify somebody..."
        return res
    return wrapped

@notifier
def original():
    print "original work"

# or: original = notifier(original)

original()

original work
notify somebody...