第2章 列表和元组

代码清单2-1 索引操作示例

# 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    = input('Year: ')
month   = input('Month  (1-12): ')
day     = 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)

运行结果如下：

Year: 2022
Month  (1-12): 10
Day (1-31): 21
October 21st, 2022

代码清单2-2 切片操作示例

# Split up a URL of the form http://www.something.com

url = input('Please enter the URL:')
domain = url[11:-4]

print("Domain name: " + domain)

运行结果如下：

Please enter the URL:http://www.python.org
Domain name: python

代码清单2-3 序列(字符串)乘法运算示例

# Prints a sentence in a centered "box" of correct width

sentence = input("Sentence: ")

screen_width = 80
text_width   = len(sentence)
box_width    = text_width + 6
left_margin  = (screen_width - box_width) // 2

print()
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)  +   '+')
print()

运行结果如下：

Sentence: He's a very naughty boy!

                         +----------------------------+
                         |                            |
                         |  He's a very naughty boy!  |
                         |                            |
                         +----------------------------+

代码清单2-4 序列成员资格示例

# Check a user name and PIN code

database = [
    ['albert',  '1234'],
    ['dilbert', '4242'],
    ['smith',   '7524'],
    ['jones',   '9843']
]

username = input('User name: ')
pin = input('PIN code: ')

if [username, pin] in database: print('Access granted')

运行结果如下：

User name: smith
PIN code: 7524
Access granted