在安装了jsonschema 3.0.1的虚拟环境（venv）中，尝试从ipython import jsonschema导致以下错误。
(venv) COMPUTER:prj user.name$ ipython
/usr/local/Cellar/ipython/7.5.0/libexec/lib/python3.7/site-packages/IPython/core/interactiveshell.py:925: UserWarning: Attempting to work in a virtualenv. If you encounter problems, please install IPython inside the virtualenv.
warn("Attempting to work in a virtualenv. If you encounter problems, please "
Python 3.7.3 (default, Mar 27 2019, 09:23:15)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.5.0 -- An enhanced Interactive Python. Type '?' for help.
[ins] In [1]: import jsonschema
---------------------------------------------------------------------------
DistributionNotFound Traceback (most recent call last)
<ipython-input-1-a1a01cfa025e> in <module>
----> 1 import jsonschema
~/prj/venv/lib/python3.7/site-packages/jsonschema/__init__.py in <module>
31
32 from pkg_resources import get_distribution
---> 33 __version__ = get_distribution(__name__).version
/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py in get_distribution(dist)
479 dist = Requirement.parse(dist)
480 if isinstance(dist, Requirement):
--> 481 dist = get_provider(dist)
482 if not isinstance(dist, Distribution):
483 raise TypeError("Expected string, Requirement, or Distribution", dist)
/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py in get_provider(moduleOrReq)
355 """Return an IResourceProvider for the named module or requirement"""
356 if isinstance(moduleOrReq, Requirement):
--> 357 return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
358 try:
359 module = sys.modules[moduleOrReq]
/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py in require(self, *requirements)
898 included, even if they were already activated in this working set.
899 """
--> 900 needed = self.resolve(parse_requirements(requirements))
901
902 for dist in needed:
/usr/local/lib/python3.7/site-packages/pkg_resources/__init__.py in resolve(self, requirements, env, installer, replace_conflicting, extras)
784 if dist is None:
785 requirers = required_by.get(req, None)
--> 786 raise DistributionNotFound(req, requirers)
787 to_activate.append(dist)
788 if dist not in req:
DistributionNotFound: The 'jsonschema' distribution was not found and is required by the application
python -c 'import jsonschema'有效。 最佳答案
如警告所示，运行以下命令可以解决此问题：
(venv) COMPUTER:prj user.name$ pip install ipython
(venv) COMPUTER:prj user.name$ venv/bin/ipython
Python 3.7.3 (default, Mar 27 2019, 09:23:15)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.5.0 -- An enhanced Interactive Python. Type '?' for help.
[ins] In [1]: import jsonschema
[ins] In [2]: