my_str = "Hello World"
func1 = getattr(__builtins__, 'len')
func1
<built-in function len>
func1()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: len() takes exactly one argument (0 given)

func1(my_str)
11

func2 = getattr(my_str, 'replace')
func2
<built-in method replace of str object at 0x102d83cc0>

func2()
Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
TypeError: replace() takes at least 2 arguments (0 given)

func2("Hello", "Yello")
'Yello World'