windows上安装命令
python -m pip install sympy
报错：
‘Connection to files.pythonhosted.org timed out. (connect timeout=15)’))
解决连接超时问题
换源：
python -m pip install sympy -i http://mirrors.aliyun.com/pypi/simple/
接下来又报错：
The repository located at mirrors.aliyun.com is not a trusted or secure host and is being ignored. If this repository is available via HTTPS it is recommended to use HTTPS instead, otherwise you may silence this warning and allow it anyways with ‘–trusted-host mirrors.aliyun.com’.
Could not find a version that satisfies the requirement sympy (from versions: )
No matching distribution found for sympy
解决host不信任问题
python -m pip install sympy -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com
接下来，提示：
Successfully installed mpmath-1.2.1 sympy-1.7.1
ok！
