Removing pip's cache?
If using pip 6.0 or newer, try adding the --no-cache-dir option (source).
If using pip older than pip 6.0, upgrade it with pip install -U pip.
Clear the cache directory where appropriate for your system
Linux and Unix
~/.cache/pip # and it respects the XDG_CACHE_HOME directory.
~/Library/Caches/pip
Windows
%LocalAppData%\pip\Cache
UPDATE
With pip 20.1 or later, you can find the full path for your operating system easily by typing this in the command line:
pip cache dir
Example output on my Ubuntu installation:
➜ pip3 cache dir
/home/tawanda/.cache/pip
From documentation at https://pip.pypa.io/en/latest/reference/pip_install.html#caching:
Starting with v6.0, pip provides an on-by-default cache which functions similarly to that of a web browser. While the cache is on by default and is designed do the right thing by default you can disable the cache and always access PyPI by utilizing the
--no-cache-diroption.