Questions #1

There are two lists - keys and values. How to make a dictionary out of them?
keys = [ 'foo' , 'bar' , 'baz' ]
vals = [ 1 , 2 , 3 ]
dict ( zip (keys, vals))
>>> { 'baz' : 3 , 'foo' : 1 , 'bar' : 2 }

The zip function returns a list of pairs of Nth elements. The dict constructor takes a list of pairs. It treats each pair as a key and a value, respectively.

Where is it faster to find an element - in a list or a set?
In a set, because a set works like a dictionary. The value is looked up by the hash of the key. Computing a hash and matching an address are operations of constant complexity, so it's common to say that looking up a dictionary is O(1).
The exception only works for very small lists up to 5 elements long. In this case, it will be faster for the interpreter to run through the list than to calculate the hash.

Functions

What are *args, **kwargs, when are they required?
The *args and **kwargs expressions are declared in the function signature. They mean that variables named args and kwargs (without asterisks) will be available inside the function. You can use other names, but this is considered bad form.
args is a tuple that accumulates positional arguments. kwargs is a dictionary of positional arguments, where key is the name of the parameter, value is the value of the parameter.
Important: if no parameters are passed to the function, the variables will be equal to an empty tuple and an empty dictionary, respectively, and not None.
Please don't confuse a tuple with a list. The next question explains why.
Why is def foo(bar=[]): bad? Give an example of a bad case. How to fix?
The function is created once when the module is loaded. Named parameters and their default values are also created once and stored in one of the function object's fields.
In our example, bar is equal to an empty list. The list is a mutable collection, so the value of bar can change from call to call. Example :