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。
1 (base) C:UsersRenyi>conda create --name yolov3 python=3.7
2 Solving environment: done
3
4
5 ==> WARNING: A newer version of conda exists. <==
6 current version: 4.5.4
7 latest version: 4.6.8
8
9 Please update conda by running
10
11 $ conda update -n base conda
12
13
14
15 ## Package Plan ##
16
17 environment location: C:UsersRenyiAnaconda3envsyolov3
18
19 added / updated specs:
20 - python=3.7
21
22
23 The following packages will be downloaded:
24
25 package | build
26 ---------------------------|-----------------
27 openssl-1.1.1b | he774522_1 5.7 MB
28 setuptools-40.8.0 | py37_0 663 KB
29 certifi-2019.3.9 | py37_0 155 KB
30 wincertstore-0.2 | py37_0 13 KB
31 wheel-0.33.1 | py37_0 57 KB
32 python-3.7.2 | h8c8aaf0_10 17.7 MB
33 ca-certificates-2019.1.23 | 0 158 KB
34 pip-19.0.3 | py37_0 1.8 MB
35 ------------------------------------------------------------
36 Total: 26.3 MB
37
38 The following NEW packages will be INSTALLED:
39
40 ca-certificates: 2019.1.23-0
41 certifi: 2019.3.9-py37_0
42 openssl: 1.1.1b-he774522_1
43 pip: 19.0.3-py37_0
44 python: 3.7.2-h8c8aaf0_10
45 setuptools: 40.8.0-py37_0
46 sqlite: 3.27.2-he774522_0
47 vc: 14.1-h0510ff6_4
48 vs2015_runtime: 14.15.26706-h3a45250_0
49 wheel: 0.33.1-py37_0
50 wincertstore: 0.2-py37_0
51
52 Proceed ([y]/n)? y
53
54
55 Downloading and Extracting Packages
56 openssl-1.1.1b | 5.7 MB | ############################################################################## | 100%
57 setuptools-40.8.0 | 663 KB | ############################################################################## | 100%
58 certifi-2019.3.9 | 155 KB | ############################################################################## | 100%
59 wincertstore-0.2 | 13 KB | ############################################################################## | 100%
60 wheel-0.33.1 | 57 KB | ############################################################################## | 100%
61 python-3.7.2 | 17.7 MB | ############################################################################## | 100%
62 ca-certificates-2019 | 158 KB | ############################################################################## | 100%
63 pip-19.0.3 | 1.8 MB | ############################################################################## | 100%
64 Preparing transaction: done
65 Verifying transaction: done
66 Executing transaction: done
67 #
68 # To activate this environment, use
69 #
70 # $ conda activate yolov3
71 #
72 # To deactivate an active environment, use
73 #
74 # $ 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
1 (base) D:PyCodeyolov3>conda activate yolov3
2
3 (yolov3) D:PyCodeyolov3>python
4 Python 3.7.2 (default, Feb 21 2019, 17:35:59) [MSC v.1915 64 bit (AMD64)] :: Anaconda, Inc. on win32
5 Type "help", "copyright", "credits" or "license" for more information.
6 >>> exit(0)
7
8 (yolov3) D:PyCodeyolov3>pip3 install -U -r requirements.txt
9 Collecting numpy (from -r requirements.txt (line 3))
10 Downloading https://files.pythonhosted.org/packages/ed/29/d97b6252591da5f8add0d25eecda296ea72729a0aad7998edba1981b47c8/numpy-1.16.2-cp36-cp36m-win_amd64.whl (11.9MB)
11 0% | | 61kB 28kB/s eta 0:07:00
12 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
1 (yolov3) D:PyCodeyolov3>python get-pip.py
2 Collecting pip
3 Using cached https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl
4 Installing collected packages: pip
5 Found existing installation: pip 19.0.3
6 Uninstalling pip-19.0.3:
7 Successfully uninstalled pip-19.0.3
8 Successfully installed pip-19.0.3
9
10 (yolov3) D:PyCodeyolov3>pip3 install -U -r requirements.txt
11 Collecting numpy (from -r requirements.txt (line 3))
12 Downloading https://files.pythonhosted.org/packages/3a/3c/515afabfe4f29bfc0a67037efaf518c33d0076b32d22ba865241cee295c4/numpy-1.16.2-cp37-cp37m-win_amd64.whl (11.9MB)
13 8% |██▌ | 962kB 6.6kB/s eta 0:27:35
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