python字符串的格式化

1.格式化为字符串%s 
>>> format = "Hello, %s. %s enough for ya?"
>>> values = ('world', 'Hot')
>>> print format % values
Hello, world. Hot enough for ya?

2.格式化为实数%f
>>> format = "Pi with three decimals: %.3f"//保留小数点后3个有效数字
>>> from math import pi//导入pi的值
>>> print format % pi
Pi with three decimals: 3.142

转换标志:  -表示左对齐，+表示转换后要加上正负号，“”空白字符表示正数之前保留空格，0表示转换值若位数不够则用0填充
*表示宽度从值元组中读出
.后面跟精度值

'%.*s' %(5,'Guido van Rossum')
'Guido'

>>> pi = 3.1415
>>> '%010.2f' % pi
'0000003.14'
>>> '%-10.2f' % pi
'3.14      '
>>> '%10.2f' % pi
'      3.14'
>>> '% 10.2f' % pi
'      3.14'
>>> '%+10.2f' % pi
'     +3.14'

width = input('Please enter width: ')

price_width = 10
item_width = width - price_width

header_format = '%-*s%*s'
format = '%-*s%*.2f'

print '=' * width

print header_format % (item_width, 'Item', price_width, 'Price')

print '-' * width

print format % (item_width, 'Apples', price_width, 0.4)
print format % (item_width, 'Pears', price_width, 0.5)
print format % (item_width, 'Cantaloupes', price_width, 1.92)
print format % (item_width, 'Dried Apricots (16 oz.)', price_width, 8)
print format % (item_width, 'Prunes (4 lbs.)', price_width, 12)

Please enter width: 35
===================================
Item                          Price
-----------------------------------
Apples                         0.40
Pears                          0.50
Cantaloupes                    1.92
Dried Apricots (16 oz.) 8.00
Prunes (4 lbs.) 12.00