ERROR: Could not find a version that satisfies the requirement numpy (from versions: none)

安装pip 出现安装失败
如下

`WARNING: The repository located at pypi.douban.com is not a trusted or secure host and is being ignored. If this repository is available via HTTPS we recommend you use HTTPS instead, otherwise you may silence this warning and allow it anyway with '--trusted-host pypi.douban.com'.
ERROR: Could not find a version that satisfies the requirement pandas (from versions: none)
ERROR: No matching distribution found for pandas`

方法1：
安装numpy 时，用下面命令

pip install numpy -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com

方法二：
找到pip.ini 文件， 一般再c:\users\用户名\AppData\Roaming\pip
把pip.ini 改成如下：（这个是加了多个镜像的源）

[global]
timeout=40
index-url=https://pypi.tuna.tsinghua.edu.cn/simple/
extra-index-url=
        https://mirrors.aliyun.com/pypi/simple/
        https://pypi.douban.com/simple
        https://pypi.mirrors.ustc.edu.cn/simple/
 
[install]
trusted-host=
        pypi.tuna.tsinghua.edu.cn
        mirrors.aliyun.com
        pypi.douban.com
        pypi.mirrors.ustc.edu.cn