Differences

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--- other:python:misc_by_jyp [2023/11/29 11:32] – [Working with paths and filenames] Improved and added pathlib example jypeter
+++ other:python:misc_by_jyp [2024/04/19 14:02] – [Data representation] Corrected link to an old JYP tutorial jypeter
@@ Line 5: / Line 5: @@
 </WRAP>
+===== Extra tutorials =====
+Only **when you have already read all the content of this page several times**, and you are looking for new ideas
+  * [[https://medium.com/@yaduvanshineelam09/ultimate-python-cheat-sheet-practical-python-for-everyday-tasks-8a33abc0892f|Ultimate Python Cheat Sheet: Practical Python For Everyday Tasks]]
 ===== Reading/setting environments variables =====
@@ Line 313: / Line 317: @@
 ['c', 'd', 'b', 'a']</code>
+===== Efficient looping with numpy, map, itertools and list comprehension =====
+<wrap hi>Big, nested, explicit ''for'' loops should be avoided at all cost</wrap>, in order to reduce a script execution time!
+  * **''numpy'' arrays** should be used when dealing with //numerical data//
+    * **Masked arrays** can be used to deal with //special cases// and remove tests from loops
+  * The built-in [[https://docs.python.org/3/library/functions.html?highlight=map#map|map]] function (and similar functions like [[https://docs.python.org/3/library/functions.html?highlight=zip#zip|zip]], [[https://docs.python.org/3/library/functions.html?highlight=filter#filter|filter]], ...) can be used to efficiently apply a function (possibly a //simple// [[https://docs.python.org/3/tutorial/controlflow.html#lambda-expressions|lambda]] function) to all the elements of a list
+    * <code>>>> my_ints = [1, 2, 3]
+>>> map(str, my_ints)
+['1', '2', '3']
+>>> map(lambda ii: str(10*ii + 5), my_ints)
+['15', '25', '35']</code>
+  * The [[https://docs.python.org/3/library/itertools.html|itertools]] module defines many more fancy iterators that can be used for efficient looping
+    * Example: replacing nested loops with [[https://docs.python.org/3/library/itertools.html#itertools.product|product]]
+      * <code>>>> it.product('AB', '01')
+<itertools.product object at 0x2b35a7b5f100>
+>>> list(it.product('AB', '01'))
+[('A', '0'), ('A', '1'), ('B', '0'), ('B', '1')]
+>>> for c1, c2 in it.product('AB', '01'):
+...   print(c1 + c2)
+...
+A0
+A1
+B0
+B1
+>>> for c1, c2 in it.product(['A', 'B'], ['0', '1']):
+...   print(c1 + c2)
+...
+A0
+A1
+B0
+B1
+>>> for c1, c2, c3 in it.product('AB', '01', '$!'):
+...   print(c1 + c2 + c3, end=', ')
+...
+A0$, A0!, A1$, A1!, B0$, B0!, B1$, B1!,</code>
+  * The [[https://docs.python.org/3/tutorial/datastructures.html?highlight=comprehension#list-comprehensions|list comprehension]] (aka //implicit loops//) can also be used to generate lists from lists
+    * Example: converting a list of integers to a list of strings\\ Note: in that case, you should rather use the ''map'' function detailed above
+      * <code>>>> my_ints = [1, 2, 3]
+>>> [ str(ii) for ii in my_ints ]
+['1', '2', '3']</code>
 ===== numpy related stuff =====
@@ Line 492: / Line 548: @@
 A few notes for a future section or page about about //data representation// (bits and bytes) on disk and in memory, vs //data format//
-FIXME Add parts (pages 28 to 37) of this [[https://wiki.lsce.ipsl.fr/pmip3/doku.php/other:python:jyp_steps#part_2|old tutorial]] to this section
+FIXME Add parts (pages 28 to 37) of this [[http://www.lsce.ipsl.fr/Phocea/file.php?class=page&file=5/pythonCDAT_jyp_2sur2_070306.pdf|old tutorial]] to this section
 ==== Base notions ====