我可以成功地将我的websockets客户端连接到websockets服务器，但是当我尝试向它发送一些消息时，它给了我这个错误：
error = 'NoneType' object has no attribute 'connected'
看来我需要使用 websockets-client 而不仅仅是 websockets，所以我尝试 pip 安装它并得到很多错误。 如何解决这些错误，以便我可以在python上使用websockets-client？
$ pip uninstall websocket
Skipping websocket as it is not installed.
$ pip install websocket-client
Requirement already satisfied: websocket-client in /usr/local/lib/python2.7/site-packages (0.44.0)
Requirement already satisfied: six in /usr/local/lib/python2.7/site-packages (from websocket-client) (1.10.0)
pyobjc-framework-mapkit 3.1.1 requires pyobjc-framework-CoreLocation>=3.1.1, which is not installed.
pyobjc-framework-syncservices 3.1.1 requires pyobjc-framework-CoreData>=3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-Accounts==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-AddressBook==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-AppleScriptKit==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-AppleScriptObjC==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-ApplicationServices==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-Automator==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-AVFoundation==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-AVKit==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CalendarStore==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CFNetwork==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CloudKit==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-Collaboration==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-Contacts==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-ContactsUI==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CoreBluetooth==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CoreData==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CoreLocation==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CoreText==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CoreWLAN==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-CryptoTokenKit==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-DictionaryServices==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-DiskArbitration==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-EventKit==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-ExceptionHandling==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-FinderSync==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-FSEvents==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-GameCenter==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-GameController==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-ImageCaptureCore==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-IMServicePlugIn==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-InputMethodKit==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-InstallerPlugins==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-InstantMessage==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-LatentSemanticMapping==3.1.1, which is not installed.
pyobjc 3.1.1 requires pyobjc_framework-LaunchServices==3.1.1, which is not installed.
mitmproxy 0.18.3 has requirement requests<2.12,>=2.9.1, but you'll have requests 2.18.4 which is incompatible.
viper 0.0.1 has requirement ethereum==2.0.4, but you'll have ethereum 1.6.1 which is incompatible.
pip应该能够为您解决缺少的依赖项，但是您遇到的两个错误在最后两行。也就是说，您对requests和ethereum的版本要求不兼容。您可以尝试更改这些软件包的版本，但它最终可能会破坏系统上的其他应用程序。
在这种情况下，我建议使用 Python 虚拟环境，这将确保程序的依赖项不会引入与系统上其他程序的依赖项不兼容。
使用虚拟环境管理包的良好参考指南位于此处：http://docs.python-guide.org/en/latest/dev/virtualenvs/