On 14/03/2015 16:33, Rustom Mody wrote:
On Saturday, March 14, 2015 at 9:45:10 PM UTC+5:30, Chris Angelico wrote:
On Sun, Mar 15, 2015 at 2:59 AM, Rustom Mody wrote:
Causing all sorts of unnecessary confusions:
An int-function returns int and a char*-functions returns char*.
Does a void-function return void??
No a void function doesn't return anything!
Ah So a void function does a longjmp?
All of which is to say that in retrospect we need (at least in imperative
programming) procedures and functions.
Best if the language supports them
Python has a broad concept of "functions/methods that return something
interesting" and "functions/methods that always return None". (The
distinction often corresponds to non-mutator and mutator methods, but
that's just convention.)
With due respect Chris, you are confused:
Sure any effective *pythonista* (who writes useful python) will have this
concept.
Python (as against pythonistas) has no such concept¹ as "function that ALWAYS
returns None"
Consider this foo
def foo(x):
... if x>0: return x-1
...
foo(3)
2
foo(-1)
As best as I can see python makes no distinction between such a foo and
the more usual function/methods that have no returns.
You can I can talk about these and distinguish them
Python has no clue about it.
Python *ALWAYS* returns None for any path through a function that
doesn't specify a return value. Taking your example.
>>> def foo(x):
... if x>0: return x-1
...
>>> import dis
>>> dis.dis(foo)
2 0 LOAD_FAST 0 (x)
3 LOAD_CONST 1 (0)
6 COMPARE_OP 4 (>)
9 POP_JUMP_IF_FALSE 20
12 LOAD_FAST 0 (x)
15 LOAD_CONST 2 (1)
18 BINARY_SUBTRACT
19 RETURN_VALUE
>> 20 LOAD_CONST 0 (None)
23 RETURN_VALUE
--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.
Mark Lawrence
--
https://mail.python.org/mailman/listinfo/python-list
