《python 从入门到精通》§2 列表和数组 §2.2通..
时间：2009-08-16 来源：oychw
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§2 列表和数组
2009-8-16
磁针石：xurongzhong#gmail.com
博客：oychw.cublog.cn
§2.1 Sequence概述
Sequence的种类：lists and tuples，strings ，Unicode strings, buffer objects, and xrange。通用操作有：indexing,slicing, adding, multiplying, and checking for membership。
lists是变长的，但是tuples不是。
>>> edward = ['Edward Gumby', 42]
>>> john = ['John Smith', 50]
>>> database = [edward, john]
>>> database
[['Edward Gumby', 42], ['John Smith', 50]]
索引：
>>> greeting = 'Hello'
>>> greeting[0]
'H'>>> greeting[-1]
'o'
>>> fourth = raw_input('Year: ')[3]
Year: 2005
>>> fourth
'5'
§2.2通用的Sequence操作
# Print out a date, given year, month, and day as numbers
months = [
'January',
'February',
'March',
'April',
'May',
'June',
'July',
'August',
'September',
'October',
'November',
'December'
]
# A list with one ending for each number from 1 to 31
endings = ['st', 'nd', 'rd'] + 17 * ['th'] \
+ ['st', 'nd', 'rd'] + 7 * ['th'] \
+ ['st']
year = raw_input('Year: ')
month = raw_input('Month (1-12): ')
day = raw_input('Day (1-31): ')
month_number = int(month)
day_number = int(day)
# Remember to subtract 1 from month and day to get a correct index
month_name = months[month_number-1]
ordinal = day + endings[day_number-1]
print month_name + ' ' + ordinal + ', ' + year
运行结果：
D:\python\Chapter02>listing2-1.py
Year: 2005
Month (1-12): 2
Day (1-31): 30
February 30th, 2005
Slicing(区间）
>>> tag = '<a href="http://www.python.org">Python web site</a>'
>>> tag[9:30]
'http://www.python.org'
>>> tag[32:-4]
'Python web site'
>>> numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
numbers[-3:-1]，[-3:0]是不合法的。必须要求第2个数在第一个数的右边。注意最后一个元素是不取的。
用空可以表示到结尾和开始
>>> numbers[-3:]
[8, 9, 10]
>>> numbers[:3]
[1, 2, 3]
In [2]: numbers[0:10]
Out[2]: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
所有元素：
>>> numbers[:]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Listing 2-2. Slicing Example
# Split up a URL of the form http://www.something.com
url = raw_input('Please enter the URL: ')
domain = url[11:-4]
print "Domain name: " + domain
运行结果：
Please enter the URL: http://www.python.org
Domain name: python
步长设置：
numbers[0:10:2]
[1, 3, 5, 7, 9]
步长不可以为0，但是可以为负，表示逆序操作。
>>> numbers[8:3:-1]
[9, 8, 7, 6, 5]
>>> numbers[10:0:-2]
[10, 8, 6, 4, 2]
添加Sequences：
同类型的可以直接使用加号相加：
>>> [1, 2, 3] + [4, 5, 6]
[1, 2, 3, 4, 5, 6]
>>> 'Hello, ' + 'world!'
'Hello, world!'
乘法：
>>> 'python' * 5
'pythonpythonpythonpythonpython'
>>> [42] * 10
[42, 42, 42, 42, 42, 42, 42, 42, 42, 42]
空值：
>>> sequence = [None] * 10
>>> sequence
[None, None, None, None, None, None, None, None, None, None]
实例2-3
Listing 2-3. Sequence (String) Multiplication Example
# Prints a sentence in a centered "box" of correct width
# Note that the integer division operator (//) only works in Python
# 2.2 and newer. In earlier versions, simply use plain division (/)
sentence = raw_input("Sentence: ")
screen_width = 80
text_width = len(sentence)
box_width = text_width + 6
left_margin = (screen_width - box_width) // 2
print ' ' * left_margin + '+' + '-' * (box_width-2) + '+'
print ' ' * left_margin + '| ' + ' ' * text_width + ' |'
print ' ' * left_margin + '| ' + sentence + ' |'
print ' ' * left_margin + '| ' + ' ' * text_width + ' |'
print ' ' * left_margin + '+' + '-' * (box_width-2) + '+'
成员关系：
>>> users = ['mlh', 'foo', 'bar']
>>> raw_input('Enter your user name: ') in users
Enter your user name: mlh
True
>>> 'P' in 'Python'
True
实例2-4
# Check a user name and PIN code
database = [
['albert', '1234'],
['dilbert', '4242'],
['smith', '7524'],
['jones', '9843']
]
username = raw_input('User name: ')
pin = raw_input('PIN code: ')
if [username, pin] in database: print 'Access granted'
长度，最大值、最小值
>>> numbers = [100, 34, 678]
>>> len(numbers)
3
>>> max(numbers)
678
>>> min(numbers)
34
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