包装_资源.get\u分布（）在导入成功时失败

Question

我正在测试Python安装。我发现了两个包，sqlite3和graph_tool，我可以import，但是它们给出了来自pkg_resources的DistributionNotFound错误（请参阅下面的控制台日志）。你知道吗

pkg_resources到底做了什么，它怎么会错过已安装的模块？你知道吗

控制台日志：

>>> import pkg_resources
>>> import graph_tool
>>> pkg_resources.get_distribution("graph_tool")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 481, in get_distribution
    dist = get_provider(dist)
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 357, in get_provider
    return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 900, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 786, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'graph_tool' distribution was not found and is required by the application

以及

>>> import sqlite3
>>> pkg_resources.get_distribution("sqlite3")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 481, in get_distribution
    dist = get_provider(dist)
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 357, in get_provider
    return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 900, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/anaconda/envs/py36/lib/python3.6/site-packages/pkg_resources/__init__.py", line 786, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'sqlite3' distribution was not found and is required by the application