Consider the following code: class Foo: def bar(self) -> Foo: return Foo() This program will actually crash at runtime if you try running it with Python: when the interpreter sees the definition of bar, the definition of Foo is not yet finished. So, since Foo has not yet been added to the global namespace, we … Read more
When Foo.__eq__ is being defined the name Foo is still unbound, because the class itself hasn’t yet been created. Remember: function arguments are evaluated at function definition time, not at function call time. From Python 3.7+ you can postpone evaluation of annotations by adding this import at the top of the module: from __future__ import … Read more
In PHP 7 they added the following: Type declarations allow functions to require that parameters are of a certain type at call time. If the given value is of the incorrect type, then an error is generated: in PHP 5, this will be a recoverable fatal error, while PHP 7 will throw a TypeError exception. … Read more
Use float only, as int is implied in that type: def my_func(number: float): PEP 484 Type Hints specifically states that: Rather than requiring that users write import numbers and then use numbers.Float etc., this PEP proposes a straightforward shortcut that is almost as effective: when an argument is annotated as having type float, an argument … Read more
Type hinting the Color class should work: def get_color_return_something(some_color: Color): print(some_color.value)
See the fifth paragraph of the abstract in the PEP you link to: While these annotations are available at runtime through the usual __annotations__ attribute, no type checking happens at runtime . Instead, the proposal assumes the existence of a separate off-line type checker which users can run over their source code voluntarily
I think you mean instanceof Iterator, PHP doesn’t have an Iterable interface. It does have a Traversable interface though. Iterator and IteratorAggregate both extend Traversable (and AFAIK they are the only ones to do so). But no, objects implementing Traversable won’t pass the is_array() check, nor there is a built-in is_iterable() function. A check you … Read more
You have a forward declaration; functions (to be bound as methods) are created before the class is, so the name Vector doesn’t yet exist. Only when all of the class body has been executed, can Python create the class object and bind the name Vector to it. Simply use a string with the name instead: … Read more
PHP 7.1 or newer (released 2nd December 2016) You can explicitly declare a variable to be null with this syntax function foo(?Type $t) { } this will result in $this->foo(new Type()); // ok $this->foo(null); // ok $this->foo(); // error So, if you want an optional argument you can follow the convention Type $t = null … Read more
There is no real difference between using a plain typing.Dict and dict, no. However, typing.Dict is a Generic type * that lets you specify the type of the keys and values too, making it more flexible: def change_bandwidths(new_bandwidths: typing.Dict[str, str], user_id: int, user_name: str) -> bool: As such, it could well be that at some … Read more