The three standard sequence operations (+,
*, []) can be performed with
lists, as well as tuples
and strings.
The + operator creates a new
list as the concatenation of the arguments.
The
>>>
["field"] + [2, 3, 4] + [9, 10, 11, 12]
['field', 2, 3, 4, 9, 10, 11, 12]
The * operator between lists
and numbers (number * list or
list * number) creates a new
list that is a number of repetitions of the input
list.
>>>
2*["pass","don't","pass"]
['pass', "don't", 'pass', 'pass', "don't", 'pass']
The [] operator selects an character or a slice from
the list. There are two forms. The first format
is
list
[
index
]
. Elements are numbered from
0 at beginning through the length. They are also number from -1 at the
end backwards to
-len(
list
).
The slice format is
list
[
start
:
end
]
. Items from
start
to
end
-1 are chosen; there will be
end
−
start
elements in the
resulting list. If
start
is omitted it is the beginning of the
list (position 0), if
end
is omitted it is the end of the
list.
In the following example, we've constructed a
list where each element is a
tuple. Each tuple could be
a pair of dice.
>>>
l=[(6, 2), (5, 4), (2, 2), (1, 3), (6, 5), (1, 4)]
>>>
l[2]
(2, 2)
>>>
print l[:3], 'split', l[3:]
[(6, 2), (5, 4), (2, 2)] split [(1, 3), (6, 5), (1, 4)]
>>>
l[-1]
(1, 4)
>>>
l[-3:]
[(1, 3), (6, 5), (1, 4)]