在Python AST中，什么时候解压缩的任务的目标是列表而不是元组？

Question

According to the GreenTreeSnakes documentation on Assignment statements :

An assignment. targets is a list of nodes, and value is a single node.

Multiple nodes in targets represents assigning the same value to each. Unpacking is represented by putting a Tuple or List within targets .

My question is, when does the unpacking put the targets in a List instead of a Tuple? The example given unpacks into a Tuple.

Answer 1

In assignments, targets can both be lists and tuples:

a, b, c = value  # assign to a tuple of names
[a, b, c] = value  # assign to a list of names

The difference is cosmetic to Python; see the Assignment statement reference documentation .

Demo:

>>> parseprint('[a, b, c] = value')
Module(body=[
    Assign(targets=[
        List(elts=[
            Name(id='a', ctx=Store()),
            Name(id='b', ctx=Store()),
            Name(id='c', ctx=Store()),
          ], ctx=Store()),
      ], value=Name(id='value', ctx=Load())),
  ])