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lists within lists

Store lists within lists

As you’ve seen, lists can hold data of mixed type. But it gets even better than
that: lists can hold collections of anything, including other lists. Simply embed
the inner list within the enclosing list as needed.
There’s only one lead
Looking closely at the movie buff’s data, it is possible to determine a structure actor listed here, but
which looks much like a list of lists: there could be more.

There’s a list of movie facts…
The Holy Grail, 1975, T erry Jones & T erry Gilliam, 91 mins
…which itself contains Graham Chapman
a list of lead actors…
Michael Palin, John Cleese, T erry Gilliam, Eric Idle & T erry Jones
…which itself
contains a list of
supporting actors.

In Python, you can turn this real list of data into code with little or no effort.
All you need to remember is that every list is a collection of items separated
from each other with commas and surrounded with square brackets. And, of
course, any list item can itself be another list:
The start of the
first, outer list

The end of all the
movies = [ lists is here.
"The Holy Grail", 1975, "Terry Jones & Terry Gilliam", 91,
["Graham Chapman",
["Michael Palin", "John Cleese", "Terry Gilliam", "Eric Idle", "Terry Jones"]]]

The start of the
second, inner list: The start of the third, inner This looks a little weird…until you
“movies[4]” inner list: “movies[4][1]” remember that there are three
opening square brackets, so there must
So, a list within a list is possible, as is a list within a list within a list (as this also be three closing ones.
example code demonstrates). In fact, it’s possible to nest lists within lists to
most any level with Python. And you can manipulate every list with its own list
methods and access it with the square bracket notation:

print(movies[4][1][3]) Eric Idle

A list within a list within a list Eric is this deeply nested, so he

can’t possibly be idle. §
18 Chapter 1