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--- other:python:misc_by_jyp [2021/07/06 13:25] – Started the command-line args section jypeter
+++ other:python:misc_by_jyp [2021/08/18 16:04] – Added pprint section jypeter
@@ Line 2: / Line 2: @@
 <WRAP center round tip 60%>
-You will find on this page some useful, but unsorted, python tips and tricks that can't fit in a section of the main [[other:python:jyp_steps|JYP's recommended steps for learning python]] page
+You will find on this page some **useful, but unsorted, python tips and tricks** that can't fit in a section of the main [[other:python:jyp_steps|JYP's recommended steps for learning python]] page
 </WRAP>
@@ Line 39: / Line 39: @@
 True</code>
+==== Working with paths and filenames ====
+If you are in a hurry, you can just use string functions to work with path and file names. But you will need some specific functions to check if a file exists, and similar operations. All these are available in 2 libraries that have similar functions. Both of these libraries can deal with Unix-type paths on Linux computers, and Windows-type paths on Windows computers
+  * [[https://docs.python.org/3/library/os.path.html|os.path]] //Common pathname manipulations//
+    * Available since... a long time! Use this if you want to avoid backward compatibility problems
+    * Some functions are directly in [[https://docs.python.org/3/library/os.html|os]] //Miscellaneous operating system interfaces//\\ e.g. [[https://docs.python.org/3/library/os.html#os.remove|os.remove]] and [[https://docs.python.org/3/library/os.html#os.rmdir|os.rmdir]]
+  * [[https://docs.python.org/3/library/pathlib.html|pathlib]] //Object-oriented filesystem paths//
+    * Available since Python version 3.4
+    * [[https://docs.python.org/3/library/pathlib.html#correspondence-to-tools-in-the-os-module|Matching pathlib, and os or os.path functions]]
+  * [[https://docs.python.org/3/library/shutil.html|High-level file operations]]
+=== Example: getting the size(s) of all the files in a directory ===
+<code>$ cd /data/jypmce/TestDir
+$ ls -l
+total 72
+-rw-r--r-- 1 jypmce ipsl 18147 Jun 25  2012 get_TS_cmip5.py
+-rw-r--r-- 1 jypmce ipsl 16152 Jun 21  2012 get_TS_cmip5.py~
+-rw-r--r-- 1 jypmce ipsl 13954 Jul  3  2012 get_TS_cmip5_regular.py
+-rw-r--r-- 1 jypmce ipsl 16539 Jun 22  2012 get_TS_cmip5_regular.py~</code>
+<code>>>> os.chdir('/data/jypmce/TestDir')
+>>> print(os.getcwd())
+/data/jypmce/TestDir
+>>> files_list = os.listdir()
+>>> files_list
+['get_TS_cmip5.py~', 'get_TS_cmip5_regular.py', 'get_TS_cmip5_regular.py~', 'get_TS_cmip5.py']
+>>> files_sizes = list(map(os.path.getsize, files_list))
+>>> files_sizes
+[16152, 13954, 16539, 18147]
+>>> sum(files_sizes)
+</code>
 ==== Using command-line arguments ====
-=== The fast but non-flexible way ===
+=== 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
@@ Line 62: / Line 95: @@
 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
+==== Using ordered dictionaries ====
+Check the [[https://realpython.com/python-ordereddict/|OrderedDict vs dict in Python: The Right Tool for the Job]] tutorial
+==== Printing a readable version of long lists or dictionaries ====
+The [[https://docs.python.org/3/library/pprint.html|pprint]] module can be used for //pretty printing// objects (lists, dictionaries, ...). It will wrap long lines in a meaningful way
+<code>>>> from collections import OrderedDict
+>>> test_dic = OrderedDict([('AWI-ESM-1-1-LR_AWI', {'r1i1p1f1': {'grid': 'gn'}}), ('CESM2_NCAR', {'r1i1p1f1': {'grid': 'gn'}}), ('IPSL-CM6A-LR_IPSL', {'r1i1p1f1': {'grid': 'gr'}, 'r1i1p1f2': {'grid': 'gr'}, 'r1i1p1f3': {'grid': 'gr'}, 'r1i1p1f4': {'grid': 'gr'}})])
+>>> print(test_dic)
+OrderedDict([('AWI-ESM-1-1-LR_AWI', {'r1i1p1f1': {'grid': 'gn'}}), ('CESM2_NCAR', {'r1i1p1f1': {'grid': 'gn'}}), ('IPSL-CM6A-LR_IPSL', {'r1i1p1f1': {'grid': 'gr'}, 'r1i1p1f2': {'grid': 'gr'}, 'r1i1p1f3': {'grid': 'gr'}, 'r1i1p1f4': {'grid': 'gr'}})])
+>>> pprint.pprint(test_dic)
+OrderedDict([('AWI-ESM-1-1-LR_AWI', {'r1i1p1f1': {'grid': 'gn'}}),
+             ('CESM2_NCAR', {'r1i1p1f1': {'grid': 'gn'}}),
+             ('IPSL-CM6A-LR_IPSL',
+              {'r1i1p1f1': {'grid': 'gr'},
+               'r1i1p1f2': {'grid': 'gr'},
+               'r1i1p1f3': {'grid': 'gr'},
+               'r1i1p1f4': {'grid': 'gr'}})])
+</code>
 /*