anaconda的python版本与本地python版本不同时的问题

在用anaconda，尤其是win下的时候，本地的python版本可能和虚拟环境中需要的python版本不同，而在虚拟环境中使用pip3安装包的时候，仍会出现版本是本地的python版本的情况，虽然并不是很清楚原因，不过记录并揣测一下。

 (base) C:\Users\Renyi>conda create --name yolov3 python=3.7
 Solving environment: done

 ==> WARNING: A newer version of conda exists. <==
   current version: 4.5.
   latest version: 4.6.

 Please update conda by running

     $ conda update -n base conda

 ## Package Plan ##

   environment location: C:\Users\Renyi\Anaconda3\envs\yolov3

   added / updated specs:
     - python=3.7

 The following packages will be downloaded:

     package                    |            build
     ---------------------------|-----------------
     openssl-1.1.1b             |       he774522_1         5.7 MB
     setuptools-40.8.          |           py37_0          KB
     certifi-2019.3.           |           py37_0          KB
     wincertstore-0.2           |           py37_0           KB
     wheel-0.33.               |           py37_0           KB
     python-3.7.2               |      h8c8aaf0_10        17.7 MB
     ca-certificates-2019.1.  |                          KB
     pip-19.0.3                 |           py37_0         1.8 MB
     ------------------------------------------------------------
                                            Total:        26.3 MB

 The following NEW packages will be INSTALLED:

     ca-certificates: 2019.1.-
     certifi:         2019.3.-py37_0
     openssl:         1.1.1b-he774522_1
     pip:             19.0.3-py37_0
     python:          3.7.-h8c8aaf0_10
     setuptools:      40.8.-py37_0
     sqlite:          3.27.-he774522_0
     vc:              14.1-h0510ff6_4
     vs2015_runtime:  14.15.-h3a45250_0
     wheel:           0.33.-py37_0
     wincertstore:    0.2-py37_0

 Proceed ([y]/n)? y

 Downloading and Extracting Packages
 openssl-1.1.1b       |  5.7 MB | ############################################################################## | %
 setuptools-40.8.    |   KB | ############################################################################## | %
 certifi-2019.3.     |   KB | ############################################################################## | %
 wincertstore-0.2     |    KB | ############################################################################## | %
 wheel-0.33.         |    KB | ############################################################################## | %
 python-3.7.2         | 17.7 MB | ############################################################################## | %
 ca-certificates- |   KB | ############################################################################## | %
 pip-19.0.3           |  1.8 MB | ############################################################################## | %
 Preparing transaction: done
 Verifying transaction: done
 Executing transaction: done
 #
 # To activate this environment, use
 #
 #     $ conda activate yolov3
 #
 # To deactivate an active environment, use
 #
 #     $ conda deactivate

这里我新建了一个python3.7的虚拟环境，提示中安装的是基于3.7的pip

 (base) D:\PyCode\yolov3>conda activate yolov3

 (yolov3) D:\PyCode\yolov3>python
 Python 3.7.2 (default, Feb  , ::) [MSC v.  bit (AMD64)] :: Anaconda, Inc. on win32
 Type "help", "copyright", "credits" or "license" for more information.
 >>> exit()

 (yolov3) D:\PyCode\yolov3>pip3 install -U -r requirements.txt
 Collecting numpy (from -r requirements.txt (line ))
   Downloading https://files.pythonhosted.org/packages/ed/29/d97b6252591da5f8add0d25eecda296ea72729a0aad7998edba1981b47c8/numpy-1.16.2-cp36-cp36m-win_amd64.whl (11.9MB)
     % |                                | 61kB 28kB/s eta ::
 Operation cancelled by user

接着我进入了刚创建完的虚拟环境，python是3.7.2版本的，然后我运行pip3来安装requirements.txt，里面有numpy，发现安装的版本是python3.6的

于是我终止了安装，并猜测，可能此时pip是更新过的，但pip3不是（未经验证） --  试了一下用pip指令就是cp37的内容了，那应该就是将pip更新成了python3.7的，但pip3没有，用get-pip.py能将pip3也更新成python3.7版本的

不过总之尝试了若干次，我发现此时更新一下pip就好了，我的更新方法还是有get-pip.py

文件地址：

https://bootstrap.pypa.io/get-pip.py

参见：

https://www.cnblogs.com/cenariusxz/p/8611796.html

 (yolov3) D:\PyCode\yolov3>python get-pip.py
 Collecting pip
   Using cached https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl
 Installing collected packages: pip
   Found existing installation: pip 19.0.
     Uninstalling pip-19.0.:
       Successfully uninstalled pip-19.0.
 Successfully installed pip-19.0.

 (yolov3) D:\PyCode\yolov3>pip3 install -U -r requirements.txt
 Collecting numpy (from -r requirements.txt (line ))
   Downloading https://files.pythonhosted.org/packages/3a/3c/515afabfe4f29bfc0a67037efaf518c33d0076b32d22ba865241cee295c4/numpy-1.16.2-cp37-cp37m-win_amd64.whl (11.9MB)
     % |██▌                             | 962kB .6kB/s eta ::

虽然看起来就是把pip-19.0.3删了再装了一次，不过这个时候再装环境，就是python3.7下的numpy了