Pyinstaller ; ModuleNotFoundError: No module named 'sklearn.utils._cython_blas'

PyInstaller uses a hook mechanism for each Python module, but sometimes it misses some internal packages so you need to provide them manually. You can use --hidden-import to add sklearn's missing modules.

pyinstaller -F --hidden-import="sklearn.utils._cython_blas" --hidden-import="sklearn.neighbors.typedefs" --hidden-import="sklearn.neighbors.quad_tree" --hidden-import="sklearn.tree._utils" Datamanager.py

Add

import sklearn.utils._cython_blas

and maybe

import sklearn.neighbors.typedefs
import sklearn.neighbors.quad_tree
import sklearn.tree
import sklearn.tree._utils

to your code.