How can a function know its calling function's decorator

Question

I have two decorators, @timeout and @retry code is like this

@timeout(seconds=1)
def func_inner(expire):
    time.sleep(expire)

@retry(
    count=2,
    message="Failed command after {expire} seconds",
)
def func(expire):
    func_inner(expire)

I just want to know how can method func() know func_inner has a decorator @timeout? Thanks in advance!

Answer 1

This code:

@timeout(seconds=1)
def func_inner(expire):
    time.sleep(expire)

Is essentially equal to:

def func_inner(expire):
    time.sleep(expire)

func_inner = timeout(seconds=1)(func_inner)

Method func simply calls func_inner(expire), which is the same as calling timeout(seconds=1)(func_inner)(expire) since the decorator has redefined the function.

Answer 2

Yes, you can see the wrapper inside the function, using inspect or globals, and you can access the wrapper object directly.

Here is a simple example showing some ways to see the wrapper inside the function.

#!/usr/bin/python
import sys
import inspect

def mydecorator(func):
    def mywrapper():
        print( 'in mywrapper' )
        func()
    return mywrapper

@mydecorator
def myfunc():
    felf = globals()[inspect.getframeinfo(inspect.currentframe()).function]
    print("** myfunc inspect : %s"%felf.__name__)

    felf = globals()[sys._getframe().f_code.co_name]
    print("** myfunc globals : %s"%felf.__name__)

    print( 'wrapper =' )
    print( myfunc )

    print( 'done myfunc' )


myfunc()

print( 'wrapper =' )
print( myfunc )

The above prints out,

in mywrapper
** myfunc inspect : mywrapper
** myfunc globals : mywrapper
wrapper =
<function mywrapper at 0x7f30df0e72a8>
done myfunc
wrapper =
<function mywrapper at 0x7f30df0e72a8>

Note that the name is not the name of your function, but instead it is the wrapper. See the inspect and getframe documentation for more about what information is available.