int is not compatable with float

[KotlinIsland]

https://mypy.readthedocs.io/en/stable/duck_type_compatibility.html

int is duck type compatible with float

No it's not:

f: float = 1
f.is_integer()

[JelleZijlstra]

Probably the best solution is to add the is_integer() method to int. This is not the right issue tracker for that, though.

[KotlinIsland]

for method in dir(float):
    try:
        getattr(int, method)
    except AttributeError as e:
        print(e)

type object 'int' has no attribute '__getformat__'
type object 'int' has no attribute '__set_format__'
type object 'int' has no attribute 'fromhex'
type object 'int' has no attribute 'hex'
type object 'int' has no attribute 'is_integer'

[KotlinIsland]

bytearray and memoryview are duck type compatible with bytes.

for method in dir(bytes):
    try:
        getattr(memoryview, method)
    except AttributeError as e:
        print(e)

type object 'memoryview' has no attribute '__add__'
type object 'memoryview' has no attribute '__contains__'
type object 'memoryview' has no attribute '__getnewargs__'
type object 'memoryview' has no attribute '__mod__'
type object 'memoryview' has no attribute '__mul__'
type object 'memoryview' has no attribute '__rmod__'
type object 'memoryview' has no attribute '__rmul__'
type object 'memoryview' has no attribute 'capitalize'
type object 'memoryview' has no attribute 'center'
type object 'memoryview' has no attribute 'count'
type object 'memoryview' has no attribute 'decode'
type object 'memoryview' has no attribute 'endswith'
type object 'memoryview' has no attribute 'expandtabs'
type object 'memoryview' has no attribute 'find'
type object 'memoryview' has no attribute 'fromhex'
type object 'memoryview' has no attribute 'index'
type object 'memoryview' has no attribute 'isalnum'
type object 'memoryview' has no attribute 'isalpha'
type object 'memoryview' has no attribute 'isascii'
type object 'memoryview' has no attribute 'isdigit'
type object 'memoryview' has no attribute 'islower'
type object 'memoryview' has no attribute 'isspace'
type object 'memoryview' has no attribute 'istitle'
type object 'memoryview' has no attribute 'isupper'
type object 'memoryview' has no attribute 'join'
type object 'memoryview' has no attribute 'ljust'
type object 'memoryview' has no attribute 'lower'
type object 'memoryview' has no attribute 'lstrip'
type object 'memoryview' has no attribute 'maketrans'
type object 'memoryview' has no attribute 'partition'
type object 'memoryview' has no attribute 'removeprefix'
type object 'memoryview' has no attribute 'removesuffix'
type object 'memoryview' has no attribute 'replace'
type object 'memoryview' has no attribute 'rfind'
type object 'memoryview' has no attribute 'rindex'
type object 'memoryview' has no attribute 'rjust'
type object 'memoryview' has no attribute 'rpartition'
type object 'memoryview' has no attribute 'rsplit'
type object 'memoryview' has no attribute 'rstrip'
type object 'memoryview' has no attribute 'split'
type object 'memoryview' has no attribute 'splitlines'
type object 'memoryview' has no attribute 'startswith'
type object 'memoryview' has no attribute 'strip'
type object 'memoryview' has no attribute 'swapcase'
type object 'memoryview' has no attribute 'title'
type object 'memoryview' has no attribute 'translate'
type object 'memoryview' has no attribute 'upper'
type object 'memoryview' has no attribute 'zfill'

[A5rocks]

FYI int being accepted as float at least is specified by PEP 484: https://www.python.org/dev/peps/pep-0484/#the-numeric-tower .

[KotlinIsland]

I think this functionality is absurd, nowhere else is duck typing used. It seems extremely inconsistent.

[sobolevn]

Related #3195 and #8363

[hauntsaninja]

typing-sig is a better place for this discussion (or bugs.python.org if the solution is to add new methods to builtins). mypy can't make changes to behaviour that is specified by PEPs.

The bool stuff is separate, since bool actually is a subtype of int at runtime.