使用命令sudo pip3 install matplotlib已知报错，用同样的命令安装numpy和opencv却没有，因此重装linux系统两次都没有解决（我是在Vmware中创建的）。报错如下：
rogn@ubuntu:~$sudo pip3 install matplotlib
Collecting numpy
Exception:
Traceback (most recent call last):
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connection.py", line 137, in _new_conn
(self.host, self.port), self.timeout, **extra_kw)
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/connection.py", line 91, in create_connection
raise err
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/connection.py", line 81, in create_connection
sock.connect(sa)
OSError: [Errno 101] Network is unreachable During handling of the above exception, another exception occurred: Traceback (most recent call last):
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 560, in urlopen
body=body, headers=headers)
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 346, in _make_request
self._validate_conn(conn)
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 787, in _validate_conn
conn.connect()
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connection.py", line 217, in connect
conn = self._new_conn()
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connection.py", line 146, in _new_conn
self, "Failed to establish a new connection: %s" % e)
requests.packages.urllib3.exceptions.NewConnectionError: <requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f3bbaa12198>: Failed to establish a new connection: [Errno 101] Network is unreachable During handling of the above exception, another exception occurred: Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/pip/basecommand.py", line 209, in main
status = self.run(options, args)
File "/usr/lib/python3/dist-packages/pip/commands/install.py", line 328, in run
wb.build(autobuilding=True)
File "/usr/lib/python3/dist-packages/pip/wheel.py", line 748, in build
self.requirement_set.prepare_files(self.finder)
File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 360, in prepare_files
ignore_dependencies=self.ignore_dependencies))
File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 512, in _prepare_file
finder, self.upgrade, require_hashes)
File "/usr/lib/python3/dist-packages/pip/req/req_install.py", line 273, in populate_link
self.link = finder.find_requirement(self, upgrade)
File "/usr/lib/python3/dist-packages/pip/index.py", line 442, in find_requirement
all_candidates = self.find_all_candidates(req.name)
File "/usr/lib/python3/dist-packages/pip/index.py", line 400, in find_all_candidates
for page in self._get_pages(url_locations, project_name):
File "/usr/lib/python3/dist-packages/pip/index.py", line 545, in _get_pages
page = self._get_page(location)
File "/usr/lib/python3/dist-packages/pip/index.py", line 648, in _get_page
return HTMLPage.get_page(link, session=self.session)
File "/usr/lib/python3/dist-packages/pip/index.py", line 757, in get_page
"Cache-Control": "max-age=600",
File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 480, in get
return self.request('GET', url, **kwargs)
File "/usr/lib/python3/dist-packages/pip/download.py", line 378, in request
return super(PipSession, self).request(method, url, *args, **kwargs)
File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 468, in request
resp = self.send(prep, **send_kwargs)
File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 576, in send
r = adapter.send(request, **kwargs)
File "/usr/share/python-wheels/CacheControl-0.11.5-py2.py3-none-any.whl/cachecontrol/adapter.py", line 46, in send
resp = super(CacheControlAdapter, self).send(request, **kw)
File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/adapters.py", line 376, in send
timeout=timeout
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 610, in urlopen
_stacktrace=sys.exc_info()[2])
File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/retry.py", line 228, in increment
total -= 1
TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'
You are using pip version 8.1.1, however version 19.0.3 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
可能当时太冲动，没有考虑太多网络问题，仔细看报错，第一个就是。
解决方法
网络问题，解决方案很简单，不用官方源改用阿里镜像。命令如下：
sudo pip3 install matplotlib -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com
效果如下：
rogn@ubuntu:~$ sudo pip3 install matplotlib -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com
The directory '/home/rogn/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/rogn/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting matplotlib
Downloading http://mirrors.aliyun.com/pypi/packages/ad/4c/0415f15f96864c3a2242b1c74041a806c100c1b21741206c5d87684437c6/matplotlib-3.0.2-cp35-cp35m-manylinux1_x86_64.whl (12.9MB)
100% |████████████████████████████████| 12.9MB 11.4MB/s
Collecting kiwisolver>=1.0.1 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/7e/31/d6fedd4fb2c94755cd101191e581af30e1650ccce7a35bddb7930fed6574/kiwisolver-1.0.1-cp35-cp35m-manylinux1_x86_64.whl (949kB)
100% |████████████████████████████████| 952kB 27.3MB/s
Collecting cycler>=0.10 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/f7/d2/e07d3ebb2bd7af696440ce7e754c59dd546ffe1bbe732c8ab68b9c834e61/cycler-0.10.0-py2.py3-none-any.whl
Collecting pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/de/0a/001be530836743d8be6c2d85069f46fecf84ac6c18c7f5fb8125ee11d854/pyparsing-2.3.1-py2.py3-none-any.whl (61kB)
100% |████████████████████████████████| 71kB 14.8MB/s
Requirement already satisfied (use --upgrade to upgrade): numpy>=1.10.0 in /usr/local/lib/python3.5/dist-packages (from matplotlib)
Requirement already satisfied (use --upgrade to upgrade): python-dateutil>=2.1 in /usr/local/lib/python3.5/dist-packages (from matplotlib)
Requirement already satisfied (use --upgrade to upgrade): setuptools in /usr/lib/python3/dist-packages (from kiwisolver>=1.0.1->matplotlib)
Requirement already satisfied (use --upgrade to upgrade): six in /usr/lib/python3/dist-packages (from cycler>=0.10->matplotlib)
Installing collected packages: kiwisolver, cycler, pyparsing, matplotlib
Successfully installed cycler-0.10.0 kiwisolver-1.0.1 matplotlib-3.0.2 pyparsing-2.3.1
You are using pip version 8.1.1, however version 19.0.3 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
就是网络慢，有时候可以慢速下载，有时直接连接失败， 好像*也不行，不知道pip3的--timeout选项变大点会不会好点。（不吐槽了，换源大法好！
Windows下同样的问题
当出现这一问题，我的Visual Studio 2017的Python3板块下使用命令pip3 install matplotlib也出错，报错如下:
C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python36_64>pip3 install matplotlib
Collecting matplotlib
Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ReadTimeoutError("HTTPSConnectionPool(host='pypi.org', port=443): Read timed out. (read timeout=15)",)': /simple/matplotlib/
Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ReadTimeoutError("HTTPSConnectionPool(host='pypi.org', port=443): Read timed out. (read timeout=15)",)': /simple/matplotlib/
Using cached https://files.pythonhosted.org/packages/b1/56/569c83515c10146fd0aa09e086816b12e301d0811048e3354a6e9b77ba9a/matplotlib-3.0.2-cp36-cp36m-win_amd64.whl
Requirement already satisfied: numpy>=1.10.0 in c:\program files (x86)\microsoft visual studio\shared\python36_64\lib\site-packages (from matplotlib) (1.16.1)
Collecting pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 (from matplotlib)
Could not find a version that satisfies the requirement pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 (from matplotlib) (from versions: )
No matching distribution found for pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 (from matplotlib)
You are using pip version 19.0.2, however version 19.0.3 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.
同样也是网络问题，用上面同样的方法：
C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python36_64>pip install matplotlib -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com
Looking in indexes: http://mirrors.aliyun.com/pypi/simple/
Collecting matplotlib
Downloading http://mirrors.aliyun.com/pypi/packages/b1/56/569c83515c10146fd0aa09e086816b12e301d0811048e3354a6e9b77ba9a/matplotlib-3.0.2-cp36-cp36m-win_amd64.whl (8.9MB)
100% |████████████████████████████████| 8.9MB 11.4MB/s
Collecting pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/de/0a/001be530836743d8be6c2d85069f46fecf84ac6c18c7f5fb8125ee11d854/pyparsing-2.3.1-py2.py3-none-any.whl (61kB)
100% |████████████████████████████████| 71kB 3.8MB/s
Collecting cycler>=0.10 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/f7/d2/e07d3ebb2bd7af696440ce7e754c59dd546ffe1bbe732c8ab68b9c834e61/cycler-0.10.0-py2.py3-none-any.whl
Requirement already satisfied: numpy>=1.10.0 in c:\program files (x86)\microsoft visual studio\shared\python36_64\lib\site-packages (from matplotlib) (1.16.1)
Collecting python-dateutil>=2.1 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/41/17/c62faccbfbd163c7f57f3844689e3a78bae1f403648a6afb1d0866d87fbb/python_dateutil-2.8.0-py2.py3-none-any.whl (226kB)
100% |████████████████████████████████| 235kB 17.1MB/s
Collecting kiwisolver>=1.0.1 (from matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/44/72/16630c3392eba03788ad87949390516bbc488e8e118047a3b824631d21a6/kiwisolver-1.0.1-cp36-none-win_amd64.whl (57kB)
100% |████████████████████████████████| 61kB 5.6MB/s
Collecting six (from cycler>=0.10->matplotlib)
Downloading http://mirrors.aliyun.com/pypi/packages/73/fb/00a976f728d0d1fecfe898238ce23f502a721c0ac0ecfedb80e0d88c64e9/six-1.12.0-py2.py3-none-any.whl
Requirement already satisfied: setuptools in c:\program files (x86)\microsoft visual studio\shared\python36_64\lib\site-packages (from kiwisolver>=1.0.1->matplotlib) (40.8.0)
Installing collected packages: pyparsing, six, cycler, python-dateutil, kiwisolver, matplotlib
Could not install packages due to an EnvironmentError: [Errno 13] Permission denied: 'c:\\program files (x86)\\microsoft visual studio\\shared\\python36_64\\Lib\\site-packages\\pyparsing.py'
Consider using the `--user` option or check the permissions. You are using pip version 19.0.2, however version 19.0.3 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.
附加：
- 阿里云 http://mirrors.aliyun.com/pypi/simple/
- 中国科技大学 https://pypi.mirrors.ustc.edu.cn/simple/
- 豆瓣(douban) http://pypi.douban.com/simple/
- 清华大学 https://pypi.tuna.tsinghua.edu.cn/simple/
参考链接：https://blog.csdn.net/qq_25964837/article/details/80295041