When editing a python file eclim will default to validating the file when it is written. Any errors will be added to the current window's location list (:help location-list) and their corresponding line number noted via Vim's sign functionality.
Python validation currently uses both the python compiler to check for syntax errors and pyflakes to perform some additional validation. To make use of the pyflakes portion of the validation you will first need to install pyflakes and make sure it is in your path.
If you don't want python files validated when saving them, you can set the g:EclimPythonValidate variable described in the configuration section below.
Regardless of whether you have validation enabled upon saving or not, the command :Validate is available to manual validate the file.
:PyLint - Runs the pylint tool on the current file, populates the quickfix list with the results (:h quickfix), and marks all the affected lines using vim's sign support.
Please see the rope docs for more information.