Unsupported operand types for > ("int" and "Number")

[jwodder]

• Are you reporting a bug, or opening a feature request? Bug
• Please insert below the code you are checking with mypy.

Sample 1 (mypy_error.py):

from numbers import Number

def is_very_large(x: Number):
    return x > 9000

Sample 2 (mypy_error2.py):

from numbers import Number

def is_foo(data: dict):
    x = data["x"]
    if isinstance(x, Number) and x < 9000:
        return True
    else:
        return False

Note: Running mypy on Sample 2 succeeds if the dict annotation is removed from data or if the first two lines of the function are replaced with def is_foo(x):.

• What is the actual behavior/output?

mypy_error2.py:5: error: Unsupported operand types for > ("int" and "Number")
mypy_error.py:4: error: Unsupported operand types for < ("int" and "Number")
Found 2 errors in 2 files (checked 2 source files)

Note that the comparison operators shown in the error messages are the opposite of what appears in the code!

• What is the behavior/output you expect? No errors, as int and Number should be fully comparable
• What are the versions of mypy and Python you are using? mypy 0.770, Python 3.7.6
  Do you see the same issue after installing mypy from Git master? Yes (commit 11c6888)
• What are the mypy flags you are using? None

[hauntsaninja]

This is false, int and Number are not fully comparable:

 λ cat test51.py  
from numbers import Number

def is_very_large(x: Number) -> None:
    assert isinstance(x, Number)
    return x > 9000

is_very_large(complex(1, -1))
λ python3 test51.py
Traceback (most recent call last):
  File "test51.py", line 7, in <module>
    is_very_large(complex(1, -1))
  File "test51.py", line 5, in is_very_large
    return x > 9000
TypeError: '>' not supported between instances of 'complex' and 'int'

The issues disappear when removing annotations because of the first point in https://mypy.readthedocs.io/en/stable/common_issues.html#no-errors-reported-for-obviously-wrong-code

You might want Real instead? This is documented here: https://docs.python.org/3/library/numbers.html#numbers.Real

[jwodder]

My mistake.