![](https://programming.dev/pictrs/image/0cfa77b8-e8cf-42e5-8fb7-71fdb0dbe63a.jpeg)
![](https://programming.dev/pictrs/image/1d99f7cb-50e7-4994-94c4-fd23f30209b7.png)
12·
10 months agoThe first one, has a implicit call to the constructor that need infer the type annotation of the result. BTW, the second form is a direct statement with a explicit type annotation, more recommended. When you see the AST of both statements, you can see the overload of calling the constructor and the use of AnnAssign (assign with type annotation) vs Assign:
thing = list[str]()
Module(
body=[
Assign(
targets=[
Name(id='thing', ctx=Store())],
value=Call(
func=Subscript(
value=Name(id='list', ctx=Load()),
slice=Name(id='str', ctx=Load()),
ctx=Load()),
args=[],
keywords=[]))],
type_ignores=[])
thing: list[str] = []
Module(
body=[
AnnAssign(
target=Name(id='thing', ctx=Store()),
annotation=Subscript(
value=Name(id='list', ctx=Load()),
slice=Name(id='str', ctx=Load()),
ctx=Load()),
value=List(elts=[], ctx=Load()),
simple=1)],
type_ignores=[])
With the
dump
function:from ast import dump, parse st = parse("thing = list[str]()") print(dump(st, indent=4)) st = parse("thing: list[str] = []") print(dump(st, indent=4))