Useful python stuff

You will find on this page some useful, but unsorted, python tips and tricks that can't fit in a section of the main JYP's recommended steps for learning python page
* Reading/setting environments variables

>>> os.environ['TMPDIR']
'/data/jypmce/climafcache'
>>> os.environ.get('SCRATCHDIR', '/data/jypmce/some_scratch_stuff')
'/data/jypmce/some_scratch_stuff'
>>> os.environ['temporary_env_var_for_THIS_script'] = 'some value'
>>> os.environ['temporary_env_var_for_THIS_script']
'some value'

* Generating (aka raising) an error. This will stop the script, unless it is called in a function, and the code calling the function explicitely catches and deals with errors

raise RuntimeError('\n\nOMG! An error! :-(\nAborting script...')

Errors and Exceptions tutorial

Built-in Exceptions reference

* Stopping a script

sys.exit('Some optional message about why we are stopping')

* Checking if a file/directory is writable by the current user

>>> os.access('/', os.W_OK)
False
>>> os.access('/home/jypmce/.bashrc', os.W_OK)
True

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