无法在Windows上安装PIP

我下载了 this 压缩文件来自 python 3.6.5 并将其解压缩到 c:\devel\opt\python .

把它添加到路径中并跟踪 these 安装PIP的说明。也尝试过 this

所以,这就是我目前为止所拥有的:

C:\>echo %PYTHON_HOME%
c:\devel\opt\python

C:\>echo %PATH%
[...]c:\devel\opt\python;c:\devel\opt\python\Scripts;[...]

C:\>python --version
Python 3.6.5

C:\>cd \devel\opt\pip

C:\devel\opt\pip>python get-pip.py
Collecting pip
[...]
Installing collected packages: pip, setuptools, wheel
Successfully installed pip-10.0.1 setuptools-39.2.0 wheel-0.31.1


C:\devel\opt\pip>cd \devel\opt\python\Scripts

C:\devel\opt\python\Scripts>dir
[...]
19/06/2018  01:18 a.m.           102.751 pip.exe
19/06/2018  01:18 a.m.           102.751 pip3.6.exe
19/06/2018  01:18 a.m.           102.751 pip3.exe
19/06/2018  01:18 a.m.           102.748 wheel.exe
[...]

C:\devel\opt\python\Scripts>pip freeze
Traceback (most recent call last):
  File "runpy.py", line 193, in _run_module_as_main
  File "runpy.py", line 85, in _run_code
  File "C:\devel\opt\python\Scripts\pip.exe\__main__.py", line 5, in <module>
ModuleNotFoundError: No module named 'pip'

C:\devel\opt\python\Scripts>python -m pip freeze
c:\devel\opt\python\python.exe: No module named pip

我正在运行Windows 7 Enterprise,SP 1

知道我会错过什么吗?