Return value of an assignment statement?

[Jeff Schwab]

bruno.desthuilliers at gmail.com wrote:
> On 21 fév, 23:06, Jeff Schwab <j... at schwabcenter.com> wrote:
>> John Henry wrote:
>>> On Feb 21, 1:48 pm, John Henry <john106he... at hotmail.com> wrote:
>>>> On Feb 21, 1:43 pm, mrstephengross <mrstevegr... at gmail.com> wrote:
>>>>> Hi all. In C, an assignment statement returns the value assigned. For
>>>>> instance:
>>>>>   int x
>>>>>   int y = (x = 3)
>>>>> In the above example, (x=3) returns 3, which is assigned to y.
>>>>> In python, as far as I can tell, assignment statements don't return
>>>>> anything:
>>>>>   y = (x = 3)
>>>>> The above example generates a SyntaxError.
>>>>> Is this correct? I just want to make sure I've understood the
>>>>> semantics.
>>>>> Thanks,
>>>>> --Steve
>>>> That's true, and I am happy that they decided to make that a syntax
>>>> error.
>>> BTW: The less obvious issues when coming from the C world are Python
>>> syntax like these:
>>> y = x = 3
>>> a = 4
>>> y = x = a
>>> print x,y
>>> a = 5
>>> print x,y
>> That's the same behavior I would expect in C, on the grounds that C
>> assignments do bit-wise copies.  What I found confusing at first was
>> that the same variable will either directly store or merely refer to an
>> object, depending on the type of the object:
>>
>>  >>> a = [ 'hello' ]
>>  >>> y = x = a
>>  >>> a += [ 'world' ]
>>  >>> print x, y
>> ['hello', 'world'] ['hello', 'world']
> 
> There's nothing like a variable "storing" anything in Python. All you
> have are names to (references to) objects binding in a namespace. Now
> the fact is that some types are mutable and other are not. In your
> above example, the augmented assignment does *not* rebind a, but
> invoke a.extend(). With integers, it would have rebind a. So while
> your observation is exact, your interpretation is wrong !-)

Thank you for the clarification.  For some reason, I had it in my head 
that ints were packed directly into the C structures that represent 
Python variables, in the same (union?) member that otherwise would store 
a pointer.