Eric Jacoboni <eric.jacob...@gmail.com>:
>>>> a_tuple[1] += [20]
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: 'tuple' object does not support item assignment
>
> [...]
>
> But, then, why a_tuple is still modified?
That's because the += operator
1. modifies the list object in place
2. tries to replace the tuple slot with the list (even though the list
hasn't changed)
It's Step 2 that raises the exception, but the damage has been done
already.
One may ask why the += operator modifies the list instead of creating a
new object. That's just how it is with lists.
BTW, try:
>>> a_tuple[1].append(20)
>>> a_tuple[1].extend([20])
Try also:
>>> a_tuple[1] = a_tuple[1]
Marko
--
https://mail.python.org/mailman/listinfo/python-list
