1, else statement
else can appear with for and while blocks.
else block will automatically run after a loop successfully terminates.
Note that the first for loop did not successfully terminate, so else block will not be executed
2, Sequence
List, Tuple, String
Note: Dict is not a sequence, because it has no order and can’t be indexed
3, Keywords Arguments are preferred to Positional Arguments
We can unpack a sequence or dict with * or ** in setting arguments
4, Mutable data structures should not be the default parameters for a function
Python’s default arguments are evaluated once when the function is defined, not each time the function is called.
5, Python searches a variable in order of [Local, Enclosed, Global, Built-in]
Locals are often inside a function.
Enclosed are often a function wrapped in another function.
Globals are often the script level.
Built-in are special names that Python reserves for itself.
