Pip: Incorrect command is shown to upgrade pip3

[paszesoft]

macOS High Sierra Version 10.13.6 Terminal App

• pip version: 19.2.3
• Python version: 3.8
• OS: High Sierra Version 10.13.6

Description
At Python 3.8 fresh (1st time - only Python 2 was present prior) install, as well as after pip3 list command, the following incorrect message is displayed:

WARNING: You are using pip version 19.2.3, however version 19.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

Expected behavior
The correct message to be displayed should read:

WARNING: You are using pip version 19.2.3, however version 19.3.1 is available.
You should consider upgrading via the 'pip**3** install --upgrade pip' command.

(missing 3 after pip)

How to Reproduce

1. Get package from https://www.python.org/ftp/python/3.8.0/python-3.8.0-macosx10.9.pkg
2. Then run https://www.python.org/ftp/python/3.8.0/python-3.8.0-macosx10.9.pkg

3. The warning is displayed:

   WARNING: You are using pip version 19.2.3, however version 19.3.1 is available.
   You should consider upgrading via the 'pip install --upgrade pip' command.`

4. Then run pip install --upgrade pip as suggested by the warning.

5. An error is displayed:

   Collecting pip3
   ERROR: Could not find a version that satisfies the requirement pip3 (from versions: none)
   ERROR: No matching distribution found for pip3

6. Then run pip3 install --upgrade pip as suggested by me above.

7. Successful installation should commence, e.g.:

   Collecting pip
   Downloading https://files.pythonhosted.org/packages/00/b6/9cfa56b4081ad13874b0c6f96af8ce16cfbc1cb06bedf8e9164ce5551ec1/pip-19.3.1-py2.py3-none-any.whl (1.4MB)
   |████████████████████████████████| 1.4MB 3.4MB/s
   Installing collected packages: pip
   Found existing installation: pip 19.2.3
   Uninstalling pip-19.2.3:
   Successfully uninstalled pip-19.2.3
   Successfully installed pip-19.3.1
   MM:~ username$ pip3 list
   Package Version

   ---

   certifi 2019.9.11
   pip 19.3.1
   setuptools 41.2.0

[paszesoft]

This issue seems to be lingering from previous versions, since I have not seen the correct resolution anywhere.

[uranusjr]

Right now it’s just hardcoded.

https://github.com/pypa/pip/blob/9ae2e6440d9fc98e91acec0a324b410fabc5452a/src/pip/_internal/self_outdated_check.py#L228-L239

Maybe we can use sys.argv[0] instead? But then how should we handle python -m pip?

[chrahunt]

It would be kind of ugly, but we could unconditionally put {sys.executable} -m pip.

[uday-patel]

pip3 install --upgrade pip
Thank you, the above worked

[vharsh]

A recent version of a windows system will have a binary akin to the which of a UNIX system, maybe we can say, $(which python) install --upgrade pip and $(where python) --upgrade pip, but this is sort of not so useful. If pip is working fine, that means python? is in $PATH or %PATH% for sure.

But to solve the 2 or 3 problem, we might want to suffix the major version from sys.version_info to pip_cmd.

Ref: https://stackoverflow.com/questions/304319/is-there-an-equivalent-of-which-on-the-windows-command-line

[uranusjr]

If pip is working fine, that means python? is in $PATH or %PATH% for sure.

This is most definitely not true. There is close to no guarantee what Python is available (or any at all) when pip is invoked. I agree with @chrahunt on unconditionally showing sys.executable; it is really the most reliable thing we can use here.