ubuntu下python3.7安装pip3安装使用各种疑难杂症

Posted 2021-09-04 奇妙之二进制

linux系统版本：ubuntu16.04
python版本：python3.7

ubuntu下安装python实在太麻烦了，牵扯各种版本，16.04默认安装了python2.7和python3.6，但python3.6太老了，很多的包都要求3.7及以上，我们今天演示如何安装python3.7以及它的pip。

如果我们直接在终端输入python，默认使用python2.7：

也可以使用python --version查看版本：

hongh@ubuntu:~$ python --version
Python 2.7.12

虽然安装了python2.7，但并没有安装pip：

hongh@ubuntu:~$ pip --version
The program 'pip' is currently not installed. You can install it by typing:
sudo apt install python-pip

提示告诉了我们安装方法：
sudo apt install python-pip
但我们不要。

pip3也同样没有安装，关于pip3和pip区别可以见：xxx。

hongh@ubuntu:~$ pip3
The program 'pip3' is currently not installed. You can install it by typing:
sudo apt install python3-pip

16.04还预置了python3.5:

hongh@ubuntu:~$ python3.5
Python 3.5.2 (default, Jan 26 2021, 13:30:48) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

我们先安装pip3：
sudo apt install python3-pip

查看pip3版本：

hongh@ubuntu:~$ pip3 --version
pip 8.1.1 from /usr/lib/python3/dist-packages (python 3.5)

除了 版本信息，还可以看到安装位置。不过这个版本很老，我们后面进行升级。

pip3是什么东西，研究下：

hongh@ubuntu:~$ which pip3
/usr/bin/pip3
hongh@ubuntu:~$ cat /usr/bin/pip3 
#!/usr/bin/python3
# GENERATED BY DEBIAN

import sys

# Run the main entry point, similarly to how setuptools does it, but because
# we didn't install the actual entry point from setup.py, don't use the
# pkg_resources API.
from pip import main
if __name__ == '__main__':
    sys.exit(main())

发现只不过是个python3脚本，调用了pip包的main函数。
而pip包放在了/usr/lib/python3/dist-packages下，注意目录是python3，说明和版本无关，python3.5和python3.7都可以使用。

pip3可以对自己进行升级，我们来升级下pip3，：
注意，pip3虽然叫pip3，但它实际对应的是pip包，所以我们：
pip3 install pip而不是pip3 install pip3
有些会让加-U或者–upgrade选项，我试了不加也可以升级，但千万不要直接升级，因为我试过，升到最新版本，python3.5不支持，

hongh@ubuntu:~$ pip3 install pip
Collecting pip
  Downloading https://files.pythonhosted.org/packages/ca/bf/4133a0e05eac641ec270bbcef30512b5ad307d7838adb994acd652cc30e3/pip-21.2.3-py3-none-any.whl (1.6MB)
    100% |████████████████████████████████| 1.6MB 25kB/s 
Installing collected packages: pip
Successfully installed pip-21.2.3

升完级pip3就用不了了：

所以最好指定下版本，我试过了，18.0可以用：

接着安装python3.7。

ubuntu16.04安装python3.7有两种方法，见：
https://hongjh.blog.csdn.net/article/details/119458920。

python3.7和pip3装完之后，我们就可以使用python3.7 -m pip install xx安装python包了：

hongh@ubuntu:~$ python3.7 -m pip install pyuavcan
Collecting pyuavcan
  Using cached https://files.pythonhosted.org/packages/00/3e/98e9c2e12fb18cc23bb8f3f4b82a09b496dbbcf286f54f38b9cba30d67cc/pyuavcan-1.2.7-py3-none-any.whl
Collecting numpy<1.20,~=1.17 (from pyuavcan)
  Using cached https://files.pythonhosted.org/packages/b1/e1/8c4c5632adaffc18dba4e03e97458dc1cb00583811e6982fc620b9d88515/numpy-1.19.5-cp37-cp37m-manylinux1_x86_64.whl
Collecting nunavut~=1.2 (from pyuavcan)

  Using cached https://files.pythonhosted.org/packages/84/93/32f766ec89a26ae9e9cc10063a92e9dc37cb8faf7b5f8213f2d60298939b/nunavut-1.4.1-66-py3-none-any.whl
Collecting pyyaml (from nunavut~=1.2->pyuavcan)
  Using cached https://files.pythonhosted.org/packages/7a/a5/393c087efdc78091afa2af9f1378762f9821c9c1d7a22c5753fb5ac5f97a/PyYAML-5.4.1-cp37-cp37m-manylinux1_x86_64.whl
Collecting pydsdl~=1.12 (from nunavut~=1.2->pyuavcan)
  Using cached https://files.pythonhosted.org/packages/fe/76/34434ff2b780959e8ad3a0358d5432f2ac379a3b89f0d4f4e0c38b237b1d/pydsdl-1.12.1-py3-none-any.whl
Installing collected packages: numpy, pyyaml, pydsdl, nunavut, pyuavcan
Successfully installed numpy nunavut pydsdl pyuavcan pyyaml
You are using pip version 8.1.1, however version 21.2.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

接着我们再给python3.7安装pip包：

hongh@ubuntu:~$ python3.7 -m pip install pip
Collecting pip
  Using cached https://files.pythonhosted.org/packages/8a/d7/f505e91e2cdea53cfcf51f4ac478a8cd64fb0bc1042629cedde20d9a6a9b/pip-21.2.2-py3-none-any.whl
Installing collected packages: pip
Successfully installed pip-21.2.2

看结果，直接安装到了最新版本。

卸载pip，从卸载输出可以看出pip安装在了/home/hongh/.local/lib/python3.7/site-packages目录，安装的包都会放在该目录下。

hongh@ubuntu:~$ python3.7 -m pip uninstall pip
Found existing installation: pip 21.2.2
Uninstalling pip-21.2.2:
  Would remove:
    /home/hongh/.local/bin/pip
    /home/hongh/.local/bin/pip3
    /home/hongh/.local/bin/pip3.7
    /home/hongh/.local/lib/python3.7/site-packages/pip-21.2.2.dist-info/*
    /home/hongh/.local/lib/python3.7/site-packages/pip/*
Proceed (Y/n)? y
  Successfully uninstalled pip-21.2.2

后续我们就可以用python3.7下的pip给python3.7安装其他包了：

python3.7 -m pip install pip

python3.7 -m pip install 包名