Negative Indexes(负索引)
>>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam[-1] 'elephant' >>> spam[-3] 'bat' >>> 'The ' + spam[-1] + ' is afraid of the ' + spam[-3] + '.' 'The elephant is afraid of the bat.'
Getting Sublists with Slices
• spam[2] is a list with an index (one integer).
• spam[1:4] is a list with a slice (two integers).
>>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam[0:4] ['cat', 'bat', 'rat', 'elephant'] >>> spam[1:3] ['bat', 'rat'] >>> spam[0:-1] ['cat', 'bat', 'rat'] >>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam[:2] ['cat', 'bat'] >>> spam[1:] ['bat', 'rat', 'elephant'] >>> spam[:] ['cat', 'bat', 'rat', 'elephant']
Getting a List’s Length with len()
>>> spam = ['cat', 'dog', 'moose'] >>> len(spam) 3
List Concatenation and List Replication
>>> [1, 2, 3] + ['A', 'B', 'C'] [1, 2, 3, 'A', 'B', 'C'] >>> ['X', 'Y', 'Z'] * 3 ['X', 'Y', 'Z', 'X', 'Y', 'Z', 'X', 'Y', 'Z'] >>> spam = [1, 2, 3] >>> spam = spam + ['A', 'B', 'C'] >>> spam [1, 2, 3, 'A', 'B', 'C']
Removing Values from Lists with del Statements
>>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> del spam[2] >>> spam ['cat', 'bat', 'elephant'] >>> del spam[2] >>> spam ['cat', 'bat']
Using for Loops with Lists
for i in [0, 1, 2, 3]: print(i)
>>> supplies = ['pens', 'staplers', 'flame-throwers', 'binders']
>>> for i in range(len(supplies)):
print('Index ' + str(i) + ' in supplies is: ' + supplies[i])
Index 0 in supplies is: pens
Index 1 in supplies is: staplers
Index 2 in supplies is: flame-throwers
Index 3 in supplies is: binders
The in and not in Operators
>>> 'howdy' in ['hello', 'hi', 'howdy', 'heyas'] True >>> spam = ['hello', 'hi', 'howdy', 'heyas'] >>> 'cat' in spam False >>> 'howdy' not in spam False >>> 'cat' not in spam True
Finding a Value in a List with the index() Method
>>> spam = ['hello', 'hi', 'howdy', 'heyas'] >>> spam.index('hello') 0 >>> spam.index('heyas') 3 >>> spam.index('howdy howdy howdy') Traceback (most recent call last): File "<pyshell#31>", line 1, in <module> spam.index('howdy howdy howdy') ValueError: 'howdy howdy howdy' is not in list
Adding Values to Lists with the append() and insert() Methods
>>> spam = ['cat', 'dog', 'bat'] >>> spam.append('moose') >>> spam ['cat', 'dog', 'bat', 'moose']
The insert() method can insert a value at any index in the list
>>> spam = ['cat', 'dog', 'bat'] >>> spam.insert(1, 'chicken') >>> spam ['cat', 'chicken', 'dog', 'bat']
Removing Values from Lists with remove()
>>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam.remove('bat') >>> spam ['cat', 'rat', 'elephant'] >>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam.remove('chicken') Traceback (most recent call last): File "<pyshell#11>", line 1, in <module> spam.remove('chicken') ValueError: list.remove(x): x not in list '如果有多个重复元素，只移除第一个' >>> spam = ['cat', 'bat', 'rat', 'cat', 'hat', 'cat'] >>> spam.remove('cat') >>> spam ['bat', 'rat', 'cat', 'hat', 'cat']
Sorting the Values in a List with the sort() Method
>>> spam = [2, 5, 3.14, 1, -7] >>> spam.sort() >>> spam [-7, 1, 2, 3.14, 5] >>> spam = ['ants', 'cats', 'dogs', 'badgers', 'elephants'] >>> spam.sort() >>> spam ['ants', 'badgers', 'cats', 'dogs', 'elephants']
