![](https://programming.dev/pictrs/image/0cfa77b8-e8cf-42e5-8fb7-71fdb0dbe63a.jpeg)
![](https://programming.dev/pictrs/image/1d99f7cb-50e7-4994-94c4-fd23f30209b7.png)
8·
11 months agoWith 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))
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))
The 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=[])
Sequence
now lives atcollections.abc
. BTW,float
is not a supertype ofint
(issubclass(int, float) == False
). Normaly, It is acceptable to useint
instead offloat
, but speaking of variance, it is more precise to usenumbers.Real
:issubclass(Integral, Real) == True issubclass(int, Real) == True issubclass(float, Real) == True issubclass(complex, Real) == False