(:source lang=python:)

"""Lists http://openbookproject.net/thinkcs/python/english2e/ch09.html """

1. A list is an ordered set of values, where each value is identified by an index.
2. The values that make up a list are called its elements.
3. Lists are similar to strings, which are ordered sets of characters, except that
4. the elements of a list can have any type.
5. use the bracket notation to create a list:

vocabulary = ["ameliorate", "castigate", "defenestrate"] numbers = [17, 123] empty = []

1. The elements of a list don't have to be the same type:

mixed_list = ["hello", 2.0, 5, [10, 20]]

1. Elements of a list are accessed using the bracket operator, the same way the characters
2. of a string.
3. Remember that the indices start at 0:

print numbers[0]

1. the index can't be larger than the length of the list - 1:

print numbers[2]

1. Any integer expression can be used as an index:

print numbers[9-8]

1. but the expression needs to be an integer value:

print numbers[1.0]

1. If an index has a negative value, it counts backward from the end of the list:

print numbers[-1] print numbers[-2]

print numbers[-3]

1. it is common to iterate through the elements of a list using a for loop:
2. (note the useage of len() to obtain the length of a list)

vocabulary = ["ameliorate", "castigate", "defenestrate"] for i in range(len(vocabulary)) :

    print vocabulary[i]

1. or:

for word in vocabulary :

    print word

1. list membership is determined using the in operator:

'castigate' in vocabulary 'word' in vocabulary

1. list operations
2. the + operator concatenates lists:

a = [1, 2, 3] b = [4, 5, 6] c = a + b print c

[0] * 4

1. Slices
2. The slice operations we saw with strings also work on lists:

a_list = ['a', 'b', 'c', 'd', 'e', 'f'] a_list[1:3] a_list[:4] a_list[3:] a_list[:]

1. Unlike strings, lists are mutable, which means we can change their elements
2. using the bracket operator:

fruit = ["banana", "apple", "quince"] fruit[0] = "pear" fruit[-1] = "orange"

1. del removes an element from a list:

a = ['one', 'two', 'three'] del a[1] print a

1. You can use a slice as an index for del:

a_list = ['a', 'b', 'c', 'd', 'e', 'f'] del a_list[1:5] print a_list

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