Windows为例：
1、点击最左下角的徽标键，点击设置按钮，并且在Windows设置里面找到应用这个功能并且点击它；
2、在应用与功能这个界面中，我们可以管理Win10本机电脑上面所有我们安装的第三方软件，为了节约寻找软件的时间，直接输入python这个名称进行应用搜索。在出现的搜索结果中，点击python3.6.5版本这个软件，然后不是点击卸载 ，我们点击修改这个按钮；
3、来到Modify Setup这个界面，点击Repair这个选项，然后耐心地等待即可，在这其中，一定不要点击右下角的Cancel选项，这个是取
消的意思；
4、耐心等待后，会出现一个结果，那就是Repair was succcesful，此时可以点击右下角的close按钮；
5、然后再次来到刚刚的应用界面，点击卸载这个按钮，会再次出现卸载这个按钮，一共点击两次；
6、然后就会出现这个Uninstall Progress ，也就是自动卸载的功能，耐心等待即可卸载完毕；
7、卸载完后，会提示我们Uninstall was successful，也就是卸载成功的意思。再次回到刚刚的应用页面，发现python3.6.5版本已经卸
载成功了，只剩下python 3.5.2版本了。
推荐学习《Python教程》！
pip install grpcio-tools
1、出现如下错误：
Traceback (most recent call last):
File "d:\usedtool\python\lib\site-packages\pip\_vendor\urllib3\response.py", line 302, in _error_catcher
yield
File "d:\usedtool\python\lib\site-packages\pip\_vendor\urllib3\response.py", line 384, in read
data = self._fp.read(amt)
File "d:\usedtool\python\lib\site-packages\pip\_vendor\cachecontrol\filewrapper.py", line 60, in read
data = self.__fp.read(amt)
File "d:\usedtool\python\lib\http\client.py", line 449, in read
n = self.readinto(b)
File "d:\usedtool\python\lib\http\client.py", line 493, in readinto
n = self.fp.readinto(b)
File "d:\usedtool\python\lib\socket.py", line 586, in readinto
return self._sock.recv_into(b)
File "d:\usedtool\python\lib\ssl.py", line 1009, in recv_into
return self.read(nbytes, buffer)
File "d:\usedtool\python\lib\ssl.py", line 871, in read
return self._sslobj.read(len, buffer)
File "d:\usedtool\python\lib\ssl.py", line 631, in read
v = self._sslobj.read(len, buffer)
socket.timeout: The read operation timed out
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "d:\usedtool\python\lib\site-packages\pip\_internal\basecommand.py", line 228, in main
status = self.run(options, args)
File "d:\usedtool\python\lib\site-packages\pip\_internal\commands\install.py", line 291, in run
resolver.resolve(requirement_set)
File "d:\usedtool\python\lib\site-packages\pip\_internal\resolve.py", line 103, in resolve
self._resolve_one(requirement_set, req)
File "d:\usedtool\python\lib\site-packages\pip\_internal\resolve.py", line 257, in _resolve_one
abstract_dist = self._get_abstract_dist_for(req_to_install)
File "d:\usedtool\python\lib\site-packages\pip\_internal\resolve.py", line 210, in _get_abstract_dist_for
self.require_hashes
File "d:\usedtool\python\lib\site-packages\pip\_internal\operations\prepare.py", line 310, in prepare_linked_requirement
progress_bar=self.progress_bar
File "d:\usedtool\python\lib\site-packages\pip\_internal\download.py", line 837, in unpack_url
progress_bar=progress_bar
File "d:\usedtool\python\lib\site-packages\pip\_internal\download.py", line 674, in unpack_http_url
progress_bar)
File "d:\usedtool\python\lib\site-packages\pip\_internal\download.py", line 898, in _download_http_url
_download_url(resp, link, content_file, hashes, progress_bar)
File "d:\usedtool\python\lib\site-packages\pip\_internal\download.py", line 618, in _download_url
hashes.check_against_chunks(downloaded_chunks)
File "d:\usedtool\python\lib\site-packages\pip\_internal\utils\hashes.py", line 48, in check_against_chunks
for chunk in chunks:
File "d:\usedtool\python\lib\site-packages\pip\_internal\download.py", line 586, in written_chunks
for chunk in chunks:
File "d:\usedtool\python\lib\site-packages\pip\_internal\utils\ui.py", line 159, in iter
for x in it:
File "d:\usedtool\python\lib\site-packages\pip\_internal\download.py", line 575, in resp_read
decode_content=False):
File "d:\usedtool\python\lib\site-packages\pip\_vendor\urllib3\response.py", line 436, in stream
data = self.read(amt=amt, decode_content=decode_content)
File "d:\usedtool\python\lib\site-packages\pip\_vendor\urllib3\response.py", line 401, in read
raise IncompleteRead(self._fp_bytes_read, self.length_remaining)
File "d:\usedtool\python\lib\contextlib.py", line 99, in __exit__
self.gen.throw(type, value, traceback)
File "d:\usedtool\python\lib\site-packages\pip\_vendor\urllib3\response.py", line 307, in _error_catcher
raise ReadTimeoutError(self._pool, None, 'Read timed out.')
pip._vendor.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Read timed out.
解决方案：pip install grpcio-tools -i https://pypi.doubanio.com/simple
后面的-i https://pypi.doubanio.com/simple即是镜像
---------------------
原文：https://blog.csdn.net/weixin_38383877/article/details/81101335 （ 侵删，感谢！ ）
【python安装】错误——“User installations are disabled via policy on the machine”解决方法一：
1、在运行里输入gpedit.msc
2、计算机配置管理>>管理模板>>windows组件>>windows Installer>>禁止用户安装
3、打开它禁用此项就可以了。
若方法一不行，请使用方法二：、
1、进入注册表目录：HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer
2、将 DisableUserInstalls 的值改为 0再安装即可
