Installing pip is not working in python < 3.6

I am trying to use these steps with bitbucket CI to deploy an application:

 script:
    - apt-get update
    - apt-get install -y python-dev
    - curl -O https://bootstrap.pypa.io/get-pip.py
    - python get-pip.py
    ... and a few more steps

However, the python get-pip.py step fails with this error:

Traceback (most recent call last):
  File "get-pip.py", line 24226, in <module>
    main()
  File "get-pip.py", line 199, in main
    bootstrap(tmpdir=tmpdir)
  File "get-pip.py", line 82, in bootstrap
    from pip._internal.cli.main import main as pip_entry_point
  File "/tmp/tmpUgc5ng/pip.zip/pip/_internal/cli/main.py", line 60
    sys.stderr.write(f"ERROR: {exc}")
                                   ^

SyntaxError: invalid syntax

Why isn’t it working now? Does it depend on the operating system?

---

_{For the equivalent issue with upgrading pip in old Python installations, see Upgrading pip fails with syntax error caused by sys.stderr.write(f”ERROR: {exc}”).}

Answer

pip 21.0 dropped support for Python 2 and 3.5. The later versions require Python 3.6+. The syntax f"" is supported by Python 3.6+.

To install pip for Python 2.7 install it from https://bootstrap.pypa.io/pip/2.7/ :

- curl -O https://bootstrap.pypa.io/pip/2.7/get-pip.py
- python get-pip.py
- python -m pip install --upgrade "pip < 21.0"

The last command is to upgrade to the latest supported version.

• For Python 2.7 the latest supported is currently pip 20.3.4.
• For Python 3.6 install from https://bootstrap.pypa.io/pip/3.6/
• For Python 3.5 install from https://bootstrap.pypa.io/pip/3.5/
• For Python 3.4 install from https://bootstrap.pypa.io/pip/3.4/
• For Python 3.4 the upgrade command is

  python -m pip install --upgrade "pip < 19.2"