pip installed pylint cannot be found

If which pylint does not find the executable but the package is installed, it is not in your PATH. Uninstall pylint you have installed with sudo and reinstall it as user, now run

$ PATH=$HOME/Library/Python/2.7/bin:$PATH which pylint

It should be found now. After you have verified pylint executable is accessible, edit your .bash_profile and add the two lines at the bottom:

PATH="${HOME}/Library/Python/2.7/bin:${PATH}"
export PATH

I have met exactly the same issue as you. Pylint is installed via pip install --user pylint since pip is managed by the system administrator and I have no permission to install packages in the system Python package directory.

The reason pylint is not found is just that you haven't added the folder where pylint is installed to the system PATH. The output of pip show --files pylint has something like the following:

Location: /home/xxx/.local/lib/python3.6/site-packages
Requires: mccabe, astroid, isort
Required-by: 
Files:
  ../../../bin/epylint
  ../../../bin/pylint
  ../../../bin/pyreverse
  ../../../bin/symilar

So pylint is installed in $HOME/.local/bin, you should add this folder to PATH:

export PATH=$HOME/.local/bin:$PATH

After that, you should be able to use pylint normally.