Import problem for Python imports module

When I recently made a decision tree with Python (decision), I met a problem that I had not encountered before, that is, "import Sklearn.tree" When everything is OK, but ' Import Sklearn ... sklearn.tree ' When the error says: Attributeerror: ' Module ' object has no attribute ' tree '.

The Python import mechanism is this, when using ' Import Sklearn ', it will only import \${sklearn_dir}/__init__.py defined objects (objectives), and then save in their own namespace (namespace) And can be used directly later; When using ' Import sklearn.tree ', Python actually imports two files, \${sklearn_dir}/__init__.py and \${sklearn_dir}/tree/__init__.py, Note that the tree is present here in the form of a subfolder.

This return to the beginning of the problem, it will be found because Sklearn.tree is a separate sub-folder/module, and in the __init__.py is not defined, so of course, can not be used in the first way to quote ~

Import problem for Python imports module