Le 30/09/2019 à 13:11, Anders Märak Leffler a écrit :
What do you mean by transformed? This is probably your understanding
already, but a further consequence of when arguments are evaluated
plus what you said about data attributes is that the fib(self, n - 1)
call will follow the standard LEGB-lookup of whatever "fib" is, from
the point of view of the function object. As far as I know, there is
no transformation of these scopes - either when it comes to creating
the class, or creating the instances. (self is just the instance,
passed as an argument.)
Cf when you change a binding:
def factorial(self, n):
... if not n:
... return 1
... else:
... return n * factorial(self, n - 1)
...
Dummy = type("DummyObject", (object, ), {"factorial" : factorial})
instance = Dummy()
def factorial(self, n):
... print("Hello!")
... return 999
...
instance.factorial(5) # Where will the call go ("old" or "new" factorial?)?
Where will possible recursive calls go (and why)?
Hello!
4995
Oh, and as others have pointed out on this list - you/whoever runs the
system sending the mail might want to change the return address.
n...@gmail.com is somewhat consistently classed as spam.
//Anders
PS. We could further complicate this by adding a call to
self.factorial in the new function, but let's not go there. :)
I understood your example, but it doesn't answer my initial question.
I try to rewrite my question:
The following code is working well and I don't really understand why
def factorial(self, n):
if not n:
return 1
else:
return n * factorial(self, n - 1)
Dummy = type("DummyObject", (object, ), {"factorial" : factorial})
instance = Dummy()
instance.factorial(3)
6 # correct
The problem is that "factorial" in line
"return n * factorial(self, n - 1)" should not have been found
because there is no factorial function defined in the current
scope.
if you use "class" keyword to define the class
class Dummy:
def factorial(self, n):
if not n:
return 1
else:
return n * factorial(self, n - 1)
instance = Dummy()
instance.factorial(3)
It generate an error because "factorial" in line
"return n * factorial(self, n - 1)" is not found.
Traceback (most recent call last):
File "<pyshell#42>", line 1, in <module>
instance.factorial(3)
File "<pyshell#40>", line 7, in factorial
return n * factorial(self, n - 1)
NameError: name 'factorial' is not defined
This is OK to me
The correct way is to write:
class Dummy:
def factorial(self, n):
if not n:
return 1
else:
return n * self.factorial(n - 1)
instance = Dummy()
instance.factorial(3)
6 # correct
So, to summarize, if you create a class with type(name, bases, dict_)
or with the "class" keyword, recursive methods can't be writen
in the same way. This is what puzzle me.
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