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--- python_notes [2023/05/22 05:04] – [difference between] raju
+++ python_notes [2024/01/03 22:15] (current) – [useful links] raju
@@ Line 2: / Line 2: @@
 ==== useful links ====
+  * [[https://tutswiki.com/python/exception-handling/ | exception handling in python]] (tutswiki.com)
+    * very easy to follow; high information density; well thought out examples
   * [[https://www.programiz.com/python-programming/online-compiler/ | Online python compiler]] (programiz.com)
     * can be useful while doing live coding interviews.
   * [[https://nedbatchelder.com/text/names.html | Facts and myths about Python names and values]] (nedbatchelder.com) - well explained.
+==== links to documentation ====
+  * os.path.basename - https://docs.python.org/3/library/os.path.html#os.path.basename
+  * continue statement - https://docs.python.org/3/reference/simple_stmts.html#the-continue-statement
 ==== validate inputs ====
 Sample snippet:
@@ Line 115: / Line 121: @@
 </code>
+==== check if something is float ====
+<code>
+% python
+Python 3.11.4 (main, Jul  5 2023, 13:45:01) [GCC 11.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> isinstance(12.0, float)
+True
+>>> isinstance(12.0, int)
+False
+>>> isinstance(12, float)
+False
+</code>
+==== check if something is int ====
+<code>
+% python
+Python 3.11.4 (main, Jul  5 2023, 13:45:01) [GCC 11.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> isinstance(12, int)
+True
+>>> isinstance(12, float)
+False
+>>> isinstance(12.0, int)
+False
+</code>
+==== Python comparisons ====
+<code>
+$ python
+Python 3.9.17 (main, Jul  5 2023, 20:47:11) [MSC v.1916 64 bit (AMD64)] on win32
+Type "help", "copyright", "credits" or "license" for more information.
+>>> 4 == True
+False
+>>> 1 == True
+True
+</code>
+==== Chained comparisons ====
+Q: In Python ''3 < 4 == True'' evaluates to False.
+<code>
+$ python
+Python 3.9.17 (main, Jul  5 2023, 20:47:11) [MSC v.1916 64 bit (AMD64)] on win32
+Type "help", "copyright", "credits" or "license" for more information.
+>>> 3 < 4 == True
+False
+</code>
+Why?
+A: The ''<'' and ''=='' are comparison operators. If a, b, c, …, y, z are expressions and op1, op2, …, opN are comparison operators, then in python, a op1 b op2 c ... y opN z is equivalent to a op1 b and b op2 c and ... y opN z, except that each expression is evaluated at most once.
+So ''3 < 4 == True'' is equivalent to ''3 < 4 and 4 == True'' which evaluates to ''True and False'' which turns out to be ''False''.
+Ref:-
+  * https://docs.python.org/3/reference/expressions.html#comparisons - describes the above rule and also gives a list of comparison operators
+==== List of comparison operators ====
+<code>
+"<" | ">" | "==" | ">=" | "<=" | "!="
+| "is" ["not"] | ["not"] "in"
+</code>
+Ref:- https://docs.python.org/3/reference/expressions.html#comparisons
 ===== tasks =====
   * [[get urls in a url]]
@@ Line 126: / Line 196: @@
 None. I prefer to use os.getenv as it is less number of characters to type.
-See also:
+To experiment, use [[https://github.com/KamarajuKusumanchi/notebooks/blob/master/python/difference%20between%20os.getenv%20vs.%20os.environ.get.ipynb | difference between os.getenv vs. os.environ.get.ipynb]] (github.com/KamarajuKusumanchi).
-  * [[https://github.com/KamarajuKusumanchi/notebooks/blob/master/python/difference%20between%20os.getenv%20vs.%20os.environ.get.ipynb | difference between os.getenv vs. os.environ.get.ipynb]] (github.com/KamarajuKusumanchi)
-  * https://stackoverflow.com/questions/16924471/difference-between-os-getenv-and-os-environ-get
+Sample usage from https://github.com/dpguthrie/yahooquery/blob/master/yahooquery/base.py#LL926C1-L936C1
+<code>
+    def __init__(self, **kwargs):
+        ...
+        username = os.getenv("YF_USERNAME") or kwargs.get("username")
+        password = os.getenv("YF_PASSWORD") or kwargs.get("password")
+        if username and password:
+            self.login(username, password)
+</code>
 ===== Snippets =====
@@ Line 261: / Line 339: @@
 print(lines)
 ['kamaraju', 'kamaraj ', 'kamara  ', 'kamar   ', 'kama    ', 'kam     ', 'ka      ', 'k       ']
+</code>
+===== programming notes =====
+==== which python executable am I running? ====
+<code>
+import sys
+print(sys.executable)
+</code>
+For example
+<code>
+$ python
+Python 3.11.5 | packaged by Anaconda, Inc. | (main, Sep 11 2023, 13:26:23) [MSC v.1916 64 bit (AMD64)] on win32
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import sys
+>>> print(sys.executable)
+C:\Users\kkusuman\AppData\Local\conda\conda\envs\py311\python.exe
 </code>