Pycharm expects ndarray out of numpy.mean instead of a float-CodePudding

Title is pretty self explanatory.

Minimal reproducible code:

import numpy
mean_sex: float = numpy.mean([1, 2, 3])
print(mean_sex)
print(type(mean_sex))

Output is:

001 | 2.0
002 | <class 'numpy.float64'>

But PyCharm does this:

I'm using: PyCharm 2022.2 (Community Edition) Build #PC-222.3345.131, built on July 27, 2022 Runtime version: 17.0.3 7-b469.32 amd64 VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o. Windows 11 10.0 GC: G1 Young Generation, G1 Old Generation Memory: 2030M Cores: 16 Non-Bundled Plugins: com.chesterccw.excelreader (2022.2.1)

CodePudding user response：

numpy.mean() can return several types (the return type is Any) and what is actually returned depends on the arguments to the function.

This is fairly typical in Python, since it is a dynamically typed language - there are no hard restrictions on what type a function returns and hinting can only get you so far.

In this case, what type is returned depends on the value of parameters like axis, which could cause the function to return a numpy.ndarray instead of a numpy.float64. Since you made it clear that you want mean_sex to explicitly contain a float, that causes the type hint you shared.

The solution is to make sure that the value coming out of numpy.mean() is actually a float, for example by passing it to float():

mean_sex: float = float(numpy.mean([1, 2, 3]))

The question here is "why bother?" You could just as easily do:

mean_sex = numpy.mean([1, 2, 3])

Is there a reason you want to specify the type for mean_sex?