the list() function

The notation [ ] is shorthand for list(). However, list() only takes one argument and returns a list. In the trivial case of list(), the argument is None and the returned list is the empty list [ ].

list() is not often used to create a list from literal objects such as strings and number since you have to wrap the input in parens or square brackets to form a single object:

["Milk" , "Cheese" , "Low fat cheese", "Beans"] is equivalent to list( ("Milk" , "Cheese" , "Low fat cheese", "Beans") )

At this point it's easier to uses the simple square bracket notation.

The power of list() comes when evaluating a generator such as range() or zip(). These functions create an object that only returns one item at a time. using list() will iterate over the object and return the results as a list.:

>>> range(5)
range(0, 5)
>>> type(range(5))
<class 'range'>
>>> list(range(5))
[0, 1, 2, 3, 4]
>>> zip([1, 2, 3], ['a', 'b', 'c'])
<zip object at 0x7f133e4924c8>
>>> list(zip([1, 2, 3], ['a', 'b', 'c']))
[(1, 'a'), (2, 'b'), (3, 'c')]

Also list() does not nest. Running list() on a list simply returns that same list:

>>> list('a')
['a']
>>> list(list(list('a')))
['a']

To get a list in a list in a list you need to use square brackets:

>>> [[['a']]]
[[['a']]]

More over, if you give list() a string, it will iterate over the string and produce a list off the characters:

>>> list('tofu')
['t', 'o', 'f', 'u']