如何看一个python的模块是否安装了

pip list

pip freeze

pip show <module_name>

pip search <module_name>

How to know if a python module is installed or not in the system: You can do a very easy test in terminal,

$ python -c "import math" $ echo $? 0 # math module exists in system $ python -c "import numpy" Traceback (most recent call last): File "<string>", line 1, in <module> ImportError: No module named numpy $ echo $? 1 # numpy module does not exist in system

In case we do not want to unwantedly import a module in question (which would happen in a trystatement) we can make use of sys.modules to test modules that are installed and were imported before.

In the python shell issue:

>>> import sys

Then test for installed modules:

>>> 'numpy' in sys.modules True >>> 'scipy' in sys.modules False