AttributeError: 'function' object has no attribute 'func_name' and python 3

Question

I downloaded the following code :

from __future__ import print_function
from time import sleep

def callback_a(i, result):
    print("Items processed: {}. Running result: {}.".format(i, result))

def square(i):
    return i * i

def processor(process, times, report_interval, callback):
    print("Entered processor(): times = {}, report_interval = {}, callback = {}".format(
    times, report_interval, callback.func_name))
    # Can also use callback.__name__ instead of callback.func_name in line above.
    result = 0
    print("Processing data ...")
    for i in range(1, times + 1):
        result += process(i)
        sleep(1)
        if i % report_interval == 0:
            # This is the call to the callback function 
            # that was passed to this function.
            callback(i, result)

processor(square, 20, 5, callback_a)

It works fine under python 2, but I get the following error under python3:

Traceback (most recent call last):
  File "test/python/cb_demo.py", line 33, in <module>
    processor(square, 20, 5, callback_a)
  File "test/python/cb_demo.py", line 21, in processor
    times, report_interval, callback.func_name))
AttributeError: 'function' object has no attribute 'func_name'

I need to work under python3.

Answer 1

That behaviour in Python 3 is expected as it was changed from Python 2. Per the documentation here:

https://docs.python.org/3/whatsnew/3.0.html#operators-and-special-methods

The function attributes named func_X have been renamed to use the __X__ form, freeing up these names in the function attribute namespace for user-defined attributes. To wit, func_closure, func_code, func_defaults, func_dict, func_doc, func_globals, func_name were renamed to __closure__, __code__, __defaults__, __dict__, __doc__, __globals__, __name__, respectively.

You will notice the mention of func_name as one of the attributes that were renamed. You will need to use __name__.

Sample code in Python 3:

>>> def foo(a):
...  print(a.__name__)
... 
>>> def c():
...  pass
... 
>>> 
>>> foo(c)
c