=> 基本语法

format_spec     ::=  [[fill]align][sign][#][0][width][grouping_option][.precision][type]
fill            ::=  <any character>
align           ::=  "<" | ">" | "=" | "^"
sign            ::=  "+" | "-" | " "
width           ::=  digit+
grouping_option ::=  "_" | ","
precision       ::=  digit+
type            ::=  "b"|"c"|"d"|"e"|"E"|"f"|"F"|"g"|"G"|"n"|"o"|"s"|"x"|"X"|"%"

=> 控制填充字符的转换方式

!r 和 !s 表示插入使用相应参数的 __repe__ 和 __str__ 函数得出的字符表示进行填充。

<<< "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
>>> "repr() shows quotes: 'test1'; str() doesn't: test2"

=> 对齐与填充

<<< '{:<30}'.format('left aligned')
'left aligned                  '
<<< '{:>30}'.format('right aligned')
'                 right aligned'
<<< '{:^30}'.format('centered')
'           centered           '
<<< '{:*^30}'.format('centered')  # use '*' as a fill char
'***********centered***********'

=> 进制转换

<<< "int: {0:d};  hex: {0:x};  oct: {0:o};  bin: {0:b}".format(42)
'int: 42;  hex: 2a;  oct: 52;  bin: 101010'

# with 0x, 0o, or 0b as prefix:
<<< "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}".format(42)
'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'

=> 数值表示

<<< '{:,}'.format(1234567890)
'1,234,567,890'

=> 小数位数与百分比

>>> points = 19
>>> total = 22
>>> 'Correct answers: {:.2%}'.format(points/total)
'Correct answers: 86.36%'

=> 格式化时间

>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'