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python - 并发使用多个 Python 版本

问题描述

我有一个需要 Python2 的脚本（speedtest-cli），但需要将 Python3 用于 Ansible。

通过 update-alternatives 我设置了“自动模式”和 Python3。我想在我的天真中，我曾以某种方式期望这会自动将 Python2 用于需要它的脚本，但它不起作用。

处理这个问题的最佳方法是什么？

Debian 克星

更新 1：尝试了 furas 的建议。它没有改变任何东西，脚本仍然抛出相同的错误......

rcd@gw:~$ python2 speedtest.py
Traceback (most recent call last):
  File "/usr/bin/speedtest-cli", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3019, in <module>
    @_call_aside
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3003, in _call_aside
    f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3032, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 655, in _build_master
    ws.require(__requires__)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 963, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 849, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'speedtest-cli==1.0.0' distribution was not found and is required by the application
Traceback (most recent call last):
  File "speedtest.py", line 12, in <module>
    ping = ping[0].replace(',', '.')
IndexError: list index out of range

请注意它如何解决 /usr/lib/python3 虽然我运行 python2 ....

rcd@gw:~$ type python2
python2 is hashed (/usr/bin/python2)
rcd@gw:~$ type python
python is /usr/bin/python
rcd@gw:~$ type python3
python3 is /usr/bin/python3
rcd@gw:~$ ls -al /usr/bin/python*
lrwxrwxrwx 1 root root      24 Jun 10 19:03 /usr/bin/python -> /etc/alternatives/python
lrwxrwxrwx 1 root root       9 Jan 24  2017 /usr/bin/python2 -> python2.7
-rwxr-xr-x 1 root root 3779512 Sep 26  2018 /usr/bin/python2.7
lrwxrwxrwx 1 root root       9 Jan 20  2017 /usr/bin/python3 -> python3.5
-rwxr-xr-x 2 root root 4751184 Sep 27  2018 /usr/bin/python3.5
lrwxrwxrwx 1 root root      33 Sep 27  2018 /usr/bin/python3.5-config -> x86_64-linux-gnu-python3.5-config
-rwxr-xr-x 2 root root 4751184 Sep 27  2018 /usr/bin/python3.5m
lrwxrwxrwx 1 root root      34 Sep 27  2018 /usr/bin/python3.5m-config -> x86_64-linux-gnu-python3.5m-config
lrwxrwxrwx 1 root root      16 Jan 20  2017 /usr/bin/python3-config -> python3.5-config
lrwxrwxrwx 1 root root      10 Jan 20  2017 /usr/bin/python3m -> python3.5m
lrwxrwxrwx 1 root root      17 Jan 20  2017 /usr/bin/python3m-config -> python3.5m-config

然后我尝试了 virtualenv ....

rcd@gw:~$ virtualenv -p /usr/bin/python2.7 venv2.7
Running virtualenv with interpreter /usr/bin/python2.7
New python executable in /home/rcd/venv2.7/bin/python2.7
Also creating executable in /home/rcd/venv2.7/bin/python
Installing setuptools, pkg_resources, pip, wheel...done.
rcd@gw:~$ source venv2.7/bin/activate

用python2.7运行，结果一模一样...

(venv2.7) rcd@gw:~$ python2 speedtest.py
Traceback (most recent call last):
  File "/usr/bin/speedtest-cli", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3019, in <module>
    @_call_aside
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3003, in _call_aside
    f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3032, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 655, in _build_master
    ws.require(__requires__)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 963, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 849, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'speedtest-cli==1.0.0' distribution was not found and is required by the application
Traceback (most recent call last):
  File "speedtest.py", line 12, in <module>
    ping = ping[0].replace(',', '.')
IndexError: list index out of range

我不知道这里发生了什么，无论我做什么，它似乎都想用 Python3 运行....

标签： pythondebiandebian-buster

解决方案

标准方法是在脚本的第一行使用shebang( #!) 来通知系统它必须使用什么程序来执行此脚本 - Python 2, Python 3, bash, perl,PHP等。

#!/full/path/to/python2

#!/full/path/to/python2.7

#!/full/path/to/python3

#!/full/path/to/python3.6

#!/full/path/to/python3.7

或更普遍和更受欢迎

#!/usr/bin/env python2

#!/usr/bin/env python2.7

#!/usr/bin/env python3

#!/usr/bin/env python3.6

#!/usr/bin/env python3.7

并且脚本必须是可执行的，所以它需要chmod +x script.py

当然你可以随时手动执行

python2   script.py

python2.7 script.py

python3   script.py

python3.6 script.py

python3.7 script.py

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