Python2.7安装OpenCV错误：TypeError: ‘NoneType’ object is not iterable

Python 安装opencv-python出现错误：

DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple
Collecting opencv-python==3.4.10.37
  Downloading https://pypi.tuna.tsinghua.edu.cn/packages/46/3e/1b61ed8e501c5d44239602c2e83d2ae43d01f9ec0a570c7cc43169c873bb/opencv-python-3.4.10.37.tar.gz (87.5MB)
     |████████████████████████████████| 87.5MB 11.8MB/s 
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  ERROR: Command errored out with exit status 1:
   command: /Users/mcj/anaconda3/envs/py2/bin/python /Users/mcj/anaconda3/envs/py2/lib/python2.7/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/tmpD3tJeD
       cwd: /private/var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/pip-install-67Cgcp/opencv-python
  Complete output (22 lines):
  Traceback (most recent call last):
    File "/Users/mcj/anaconda3/envs/py2/lib/python2.7/site-packages/pip/_vendor/pep517/_in_process.py", line 257, in <module>
      main()
    File "/Users/mcj/anaconda3/envs/py2/lib/python2.7/site-packages/pip/_vendor/pep517/_in_process.py", line 240, in main
      json_out['return_val'] = hook(**hook_input['kwargs'])
    File "/Users/mcj/anaconda3/envs/py2/lib/python2.7/site-packages/pip/_vendor/pep517/_in_process.py", line 91, in get_requires_for_build_wheel
      return hook(config_settings)
    File "/private/var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/pip-build-env-RJWX8u/overlay/lib/python2.7/site-packages/setuptools/build_meta.py", line 146, in get_requires_for_build_wheel
      return self._get_build_requires(config_settings, requirements=['wheel'])
    File "/private/var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/pip-build-env-RJWX8u/overlay/lib/python2.7/site-packages/setuptools/build_meta.py", line 127, in _get_build_requires
      self.run_setup()
    File "/private/var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/pip-build-env-RJWX8u/overlay/lib/python2.7/site-packages/setuptools/build_meta.py", line 243, in run_setup
      self).run_setup(setup_script=setup_script)
    File "/private/var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/pip-build-env-RJWX8u/overlay/lib/python2.7/site-packages/setuptools/build_meta.py", line 142, in run_setup
      exec(compile(code, __file__, 'exec'), locals())
    File "setup.py", line 448, in <module>
      main()
    File "setup.py", line 99, in main
      % {"ext": re.escape(sysconfig.get_config_var("EXT_SUFFIX"))}
    File "/Users/mcj/anaconda3/envs/py2/lib/python2.7/re.py", line 210, in escape
      s = list(pattern)
  TypeError: 'NoneType' object is not iterable
  ----------------------------------------
ERROR: Command errored out with exit status 1: /Users/mcj/anaconda3/envs/py2/bin/python /Users/mcj/anaconda3/envs/py2/lib/python2.7/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /var/folders/_q/nw2x15wx38l8hngtj0x2h3rw0000gn/T/tmpD3tJeD Check the logs for full command output.

解决办法：

主要原因是Python 安装的OpenCV版本的问题，只需要改为：

pip install opencv-python==4.2.0.32

解决后：

Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple
Collecting opencv-python==4.2.0.32
  Downloading https://pypi.tuna.tsinghua.edu.cn/packages/56/ff/59c8c21163eafc63261d13792f8303ac45bcb0edd7b098f9f6b91fdbe215/opencv_python-4.2.0.32-cp27-cp27m-macosx_10_9_x86_64.whl (47.9MB)
     |████████████████████████████████| 47.9MB 367kB/s 
Collecting numpy>=1.11.1
  Downloading https://pypi.tuna.tsinghua.edu.cn/packages/09/96/84cf406fe7d589f3dba9fc0f737e65985a3526c6d8c783f02d4b5a10825d/numpy-1.16.6-cp27-cp27m-macosx_10_9_x86_64.whl (13.9MB)
     |████████████████████████████████| 13.9MB 11.0MB/s 
Installing collected packages: numpy, opencv-python
Successfully installed numpy-1.16.6 opencv-python-4.2.0.32