Type hint for NumPy ndarray dtype?

Question

I would like a function to include a type hint for NumPy ndarray\'s alongside with its dtype.

With lists, for example, one could do the fol

Answer 1

Check out data-science-types package.

pip install data-science-types

MyPy now has access to Numpy, Pandas, and Matplotlib stubs. Allows scenarios like:

# program.py

import numpy as np
import pandas as pd

arr1: np.ndarray[np.int64] = np.array([3, 7, 39, -3])  # OK
arr2: np.ndarray[np.int32] = np.array([3, 7, 39, -3])  # Type error

df: pd.DataFrame = pd.DataFrame({'col1': [1,2,3], 'col2': [4,5,6]}) # OK
df1: pd.DataFrame = pd.Series([1,2,3]) # error: Incompatible types in assignment (expression has type "Series[int]", variable has type "DataFrame")

Use mypy like normal.

$ mypy program.py