Building lists – literals, appending, and comprehensions

If we've decided to create a collection that uses an item's position—a list—we have several ways of building this structure. We'll look at a number of ways we can build a list object from individual items.

In some cases, we'll need a list because it allows duplicate values. A great many statistical operations don't require knowing the position of an item. A multiset would be useful for this, but we don't have this as a built-in structure; it's very common to use a list instead of a multiset.

Getting ready

Let's say we need to do some statistical analyses on some file sizes. Here's a short script that will provide us with the sizes of some files:

>>> import pathlib 
>>> home = pathlib.Path('source') 
>>> for path in home.glob('*/index.rst'): 
...     print(path.stat().st_size, path.parent) 
2353 source/ch_01_numbers_strings_and_tuples 
2889 source/ch_02_statements_and_syntax 
2195...