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--- other:python:misc_by_jyp [2021/06/30 17:20] – jypeter
+++ other:python:misc_by_jyp [2021/07/06 13:49] – [Using command-line arguments] added getopt, optparse and argparse jypeter
@@ Line 5: / Line 5: @@
 </WRAP>
- * Reading/setting environments variables\\ <code>>>> os.environ['TMPDIR']
+==== Reading/setting environments variables ====
+<code>>>> os.environ['TMPDIR']
 '/data/jypmce/climafcache'
 >>> os.environ.get('SCRATCHDIR', '/data/jypmce/some_scratch_stuff')
@@ Line 14: / Line 17: @@
 </code>
- * 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
+==== 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
     * <code>raise RuntimeError('\n\nOMG! An error! :-(\nAborting script...')</code>
     * [[https://docs.python.org/3/tutorial/errors.html|Errors and Exceptions tutorial]]
     * [[https://docs.python.org/3/library/exceptions.html|Built-in Exceptions reference]]
- * Stopping a script\\ <code>sys.exit('Some optional message about why we are stopping')</code>
- * Checking if a file/directory is writable by the current user\\ <code>>>> os.access('/', os.W_OK)
+==== 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
+<code>sys.exit('Some optional message about why we are stopping')</code>
+==== Checking if a file/directory is writable by the current user ====
+<code>>>> os.access('/', os.W_OK)
 False
 >>> os.access('/home/jypmce/.bashrc', os.W_OK)
 True</code>
+==== Using command-line arguments ====
+=== The extremely easy but non-flexible way: sys.argv ===
+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:
+<code>#!/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)</code>
+<code>$ python argv_test.py
+Number of script arguments (including script name) = 1
+argv_test.py
+$ python argv_test.py tas tas_tes.nc
+Number of script arguments (including script name) = 3
+argv_test.py
+tas
+tas_tes.nc</code>
+=== The C-style way: getopt ===
+Use [[https://docs.python.org/3/library/getopt.html|getopt]] (//C-style parser for command line options//)
+=== The deprecated Python way: optparse ===
+[[https://docs.python.org/3/library/optparse.html|optparse]] (//parser for command line options//) is **deprecated since Python version 3.2**! You should now use argparse (check [[https://docs.python.org/3/library/argparse.html#upgrading-optparse-code|Upgrading optparse code]] for converting from ''optparse'' to ''argparse'')
+=== The current Python way: argparse ===
+[[https://docs.python.org/3/library/argparse.html|argparse]] (//parser for command-line options, arguments and sub-commands//) is available since Python version 3.2
 /*
- * tip template\\ <code>Some code</code>
+==== Tip template ====
+<code>Some code</code>
  */