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Table of Contents
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...')
Stopping a script
A user can use CTRL-C or kill to stop a script, or CTRL-Z to suspend it temporarily (use fg to resume a suspended script). The code below can be used by the script itself to interrupt its execution, instead of raising an error
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
Using command-line arguments
The fast but non-flexible way
The name of a script, the number of arguments (including the name of the script), and the arguments (as strings) can be accessed through the sys.argv strings' list
Simple argv_test.py test script:
#!/usr/bin/env python
import sys
nb_args = len(sys.argv)
print('Number of script arguments (including script name) =', nb_args)
for idx, val in enumerate(sys.argv):
print(idx, val)
$ python argv_test.py Number of script arguments (including script name) = 1 0 argv_test.py $ python argv_test.py tas tas_tes.nc Number of script arguments (including script name) = 3 0 argv_test.py 1 tas 2 tas_tes.nc
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