Something in the function tutorial confused me.

[Alex Martelli]

Neil Cerutti <horpner at yahoo.com> wrote:
   ...
> The Python Language Reference seems a little confused about the
> terminology.
> 
>   3.4.7 Emulating numeric types
>   6.3.1 Augmented assignment statements
> 
> The former refers to "augmented arithmetic operations", which I
> think is a nice terminology, since assignment is not necessarily
> taking place. Then the latter muddies the waters.

Assignment *IS* "necessarily taking place"; if you try the augmented
assignment on something that DOESN'T support assignment, you'll get an
exception.  Consider:

>>> tup=([],)
>>> tup[0] += ['zap']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

Tuples don't support item ASSIGNMENT, and += is an ASSIGNMENT, so tuples
don't allow a += on any of their items.

If you thought that += wasn't an assignment, this behavior and error
message would be very problematic; since the language reference ISN'T
confused and has things quite right, this behavior and error message are
perfectly consistent and clear.


Alex