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--- other:python:misc_by_jyp [2022/12/12 14:50] – Improved by changing the sections' levels jypeter
+++ other:python:misc_by_jyp [2023/04/26 17:50] – Started a Data represenation section jypeter
@@ Line 32: / Line 32: @@
 <code>sys.exit('Some optional message about why we are stopping')</code>
+===== Data representation =====
+A few notes for a future section or page about about data representation (bits and bytes) on disk and in memory, vs data format
+  * Binary data representation
+    * [[https://en.wikipedia.org/wiki/Bit_numbering|Bit numbering]]
+    * [[https://en.wikipedia.org/wiki/Endianness|Endianness]]
+    * [[https://en.wikipedia.org/wiki/Integer_(computer_science)|Integers]]
+      * Using [[https://en.wikipedia.org/wiki/Two%27s_complement|two's complement]] for negative integers
+      * Range:
+        * 4-byte integers: −2,147,483,648 to 2,147,483,647
+        * 8-byte integers: −9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
+    * [[https://en.wikipedia.org/wiki/IEEE_754|Floating point numbers]] (//IEEE 754// standard)
+      * Range:
+        * 4-byte float: ~8 significant digits ^10E±38
+          * See also [[https://en.wikipedia.org/wiki/Single-precision_floating-point_format|Single-precision floating-point format|Single-precision floating-point format]]
+        * 8-byte float: ~15 significant digits ^10E±308
+  * Array addressing
+  * disk and ram usage: how to check the usage (available ram and disk), best practice on multi-user systems (how much allowed?)
+    * ''du'', ''df'', ''cat /proc/meminfo'', ''top''
+  * understanding and reverse-engineering //binary// format
+    * ''od'', ''strings''
+  * binary vs text format: ascii, utf, raw
+    * text related functions in python: ''str'', ''int'', ''float'', ''ord'', ...
+      * lists conversion with ''map'' and ''join''
+  * Misc : ''md5sum''
 ===== Checking if a file/directory is writable by the current user =====
@@ Line 43: / Line 73: @@
 ===== Playing with strings =====
-==== Filenames, etc... ====
-Check [[other:python:misc_by_jyp#working_with_paths_and_filenames|Working with paths and filenames]] and [[other:python:misc_by_jyp#generating_file_names|Generating file names]]
-==== Splitting strings ====
+==== Splitting (complex) strings ====
 It's easy to split a string with multiple blank delimiters, or a specific delimiter, but it can be harder to deal with sub-strings
@@ Line 257: / Line 284: @@
 Note: a configuration file is also a way to easily store and exchange text data !
+===== Working with global variables =====
+There is a good chance you don't actually want/need a //global// variable. Be sure to use the ''global'' statement correctly if you want to avoid side-effects...
+  * [[https://docs.python.org/3/faq/programming.html?highlight=global#why-am-i-getting-an-unboundlocalerror-when-the-variable-has-a-value|Using (and changing) a global variable inside a script or module]]
+    * Simple module example\\ <code>_myvar = 10
+def set_myvar(new_val):
+    # Note: need to explicitly define a global variable (of a module)
+    # as 'global' BEFORE changing its value in a function!
+    # Otherwise, the value will not be REdefined outside the function
+    global _myvar
+    _myvar = new_val
+def get_myvar():
+    return _myvar
+def myfunc(nb_repeat = 10):
+    print(nb_repeat * _myvar)</code>
+  * [[https://docs.python.org/3/faq/programming.html?highlight=global#how-do-i-share-global-variables-across-modules|Sharing global variables across modules]]
 ===== Sorting =====
@@ Line 435: / Line 483: @@
 >>> np.add.reduceat(np.sort(vals), slices_indices)
 array([3. , 4.5, 8. ])</code>
+===== matplotlib related stuff =====
+==== Working with time axes (and ticks) ====
+If you have problems setting the limits of a time axis, choosing the ticks' locations, or specifying the style of the labels, you should check the:
+  * [[https://matplotlib.org/stable/gallery/index.html#ticks|Ticks examples' gallery]]
+  * [[https://matplotlib.org/stable/gallery/text_labels_and_annotations/date.html|Date tick labels example]]