Are tuples immutable?

[perfringo]

This can be also worth of knowing about tuples immutability:

>>> spam = (1, [2, 3])
>>> spam[1] += [4, 5]            # will throw error but still mutate list within tuple
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> spam
(1, [2, 3, 4, 5])

[python_user_n]

@perfringo thanks. It's good to know about details like this.

[buran]

It's good to know about details like this.

Note that this apply only for augmented arithmetic assignment +=, but not for "regular" addition/assignment, i.e.

>>> spam = (1, [2, 3])
>>> spam[1] = spam[1] + [4, 5]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> spam[1]
[2, 3]
>>>

As you can see in this case there is exception and the mutable object is not changed.

Read Why does a_tuple[i] += [‘item’] raise an exception when the addition works? for extended discussion and in-depth explanation.

[python_user_n]

@buran, Indeed. I remember about '+=' augmented operator when I was comparing it to a '+' concatenation.