在windows系统下通过安装Anaconda的方式安装的python使用中发现不能再通过pip安装python包。只能通过conda install packname 的方法，导致很多conda不支持的包无法安装(我遇到的是 request)
解决方法：打开Anaconde prompt
在该prompt中使用pip而不是命令行或者powershell中使用pip
问题顺利解决。
例如：在命令行pip install dlib 报错
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.")) - skipping
在Anaconde prompt 运行 pip install requests 顺利安装完成
Requirement already satisfied: requests in e:\anaconda\lib\site-packages (2.21.0)
Requirement already satisfied: chardet<3.1.0,>=3.0.2 in e:\anaconda\lib\site-packages (from requests) (3.0.4)
Requirement already satisfied: certifi>=2017.4.17 in e:\anaconda\lib\site-packages (from requests) (2018.11.29)
Requirement already satisfied: idna<2.9,>=2.5 in e:\anaconda\lib\site-packages (from requests) (2.8)
Requirement already satisfied: urllib3<1.25,>=1.21.1 in e:\anaconda\lib\site-packages (from requests) (1.24.1)