Mutable default values example - TypeError: 'int' object is not iterable

[dec1]

Documentation

The example:

dataclasses.html#mutable-default-values

@dataclass
class D:
    x: list = []      # This code raises ValueError
    def add(self, element):
        self.x += element

not only raises the ValueError being discussed, but also an unwanted TypeError when you call add(), that distracts from the point of the example.
Would be better to call append() to add a single element to the list

Linked PRs

• gh-116535: Fix distracting "TypeError" in example code #116536
• gh-116535: Fix distracting "TypeError" in example code #116538
• [3.12] gh-116535: Fix distracting "TypeError" in example code (gh-116538) #116551
• [3.11] gh-116535: Fix distracting "TypeError" in example code (gh-116538) #116552

[Privat33r-dev]

Your point is valid. And what's more, using .append() instead of += would match the style used in the first example (without dataclasses), which is going to increase consistency and remove distractions.

[ericvsmith]

Merged. Thanks!