Repository navigation
Float multiplication of numpy.ndarray in lambda is incorrectly analysed #8001
Description
Note: if you are reporting a wrong signature of a function or a class in
the standard library, then the typeshed tracker is better suited
for this report: https://github.com/python/typeshed/issues
Please provide more information to help us understand the issue:
- Are you reporting a bug, or opening a feature request?
Bug.
- Please insert below the code you are checking with mypy,
or a mock-up repro if the source is private. We would appreciate
if you try to simplify your case to a minimal repro.
from typing import NewType, Tuple, Deque
import numpy as np
class Point(np.ndarray):
def __new__(cls, x: float, y: float) -> np.ndarray:
return np.array((x, y), dtype=np.float32)
Nose = NewType("Nose", Tuple[Point, ...])
def average_position(positions: Deque) -> Nose:
factor = 1.0 / len(positions)
point_sum = [Point(0.0, 0.0) for _ in range(10)]
for nose in positions:
for i, point in enumerate(nose):
point_sum[i] += point
avg_pos = Nose(tuple(map(lambda p: factor * p, point_sum)))
return avg_pos
def average_position_with_multiply(positions: Deque) -> Nose:
factor = 1.0 / len(positions)
point_sum = [Point(0.0, 0.0) for _ in range(10)]
for nose in positions:
for i, point in enumerate(nose):
point_sum[i] += point
avg_pos = Nose(tuple(map(lambda p: np.multiply(factor, p), point_sum)))
return avg_pos- What is the actual behavior/output?
Mypy gives the errors below:
bug.py:20: error: Argument 1 to "map" has incompatible type "Callable[[Point], float]"; expected "Callable[[Point], Point]"
bug.py:20: error: Incompatible return value type (got "float", expected "Point")
Found 2 errors in 1 file (checked 1 source file)In the lambda in average_position(), mypy incorrectly (?) determines the type as Callable[[Point], float], while using the NumPy function np.multiply() (which does the same thing) gives no error. Both functions output the same correct value.
-
What is the behavior/output you expect?
There should be no error. -
What are the versions of mypy and Python you are using?
Do you see the same issue after installing mypy from Git master?
mypy==0.740
Python 3.8.0
- What are the mypy flags you are using? (For example --strict-optional)
[mypy]
python_version = 3.8
[mypy-cv2,dlib,numpy]
ignore_missing_imports = TrueI am unsure if this is actually an error, or if I've done something wrong somewhere, but both functions run and output correctly.
Activity
JukkaL commentedon Nov 22, 2019
The root of the problem is that mypy incorrectly infers the type of multiplying
Pointby a float. Here's a shorter example:As a workaround, you can try installing stubs for numpy (https://github.com/numpy/numpy-stubs).
Fix incorrect type inference when inherited from Any class (#8019)
ilevkivskyi commentedon Nov 13, 2022
It looks like #8019 didn't actually fix this issue, at least Jukka's simple example above still fails. It accidentally passes in tests (see
testOpWithInheritedFromAny) because in builtins fixturesfloatdoesn't have__add__(). I am going to mark itxfailin #14077 (since I need that__add__()that actually present in real builtins stubs, for my tests).ilevkivskyi commentedon Nov 13, 2022
cc @TH3CHARLie @msullivan