函数说明
string.format()，格式化字符串。
语法
格式化字符串包含由大括号{}围住的“替代域”，在大括号外的文本内容直接复制到输出的字符串里。string.format()的语法类似于%，不同之处在于在此使用{}和：两个符号替代。例如， '%03.2f' 对应为'{:03.2f}'。string.format()的语法为
format_spec ::= [[fill]align][sign][#][0][width][,][.precision][type]fill ::= <any character>align ::= "<" | ">" | "=" | "^"sign ::= "+" | "-" | " "width ::= integerprecision ::= integertype ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
实例
通过位置访问参数（arguments）
>>> '{0}, {1}, {2}'.format('a', 'b', 'c')'a, b, c'>>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+ only'a, b, c'>>> '{2}, {1}, {0}'.format('a', 'b', 'c')'c, b, a'>>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence'c, b, a'>>> '{0}{1}{0}'.format('abra', 'cad') # arguments' indices can be repeated'abracadabra'通过变量的名字访问参数
>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')'Coordinates: 37.24N, -115.81W'>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)'Coordinates: 37.24N, -115.81W'
访问参数的属性
>>> c = 3-5j>>> ('The complex number {0} is formed from the real part {0.real} '... 'and the imaginary part {0.imag}.').format(c)'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'>>> class Point:... def __init__(self, x, y):... self.x, self.y = x, y... def __str__(self):... return 'Point({self.x}, {self.y})'.format(self=self)...>>> str(Point(4, 2))'Point(4, 2)'
访问参数的项（item）
>>> coord = (3, 5)>>> 'X: {0[0]}; Y: {0[1]}'.format(coord)'X: 3; Y: 5'
对齐文本并指定特定的宽度
>>> '{:<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***********'使用%+f, %-f, 和 % f 并指定符号:
>>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it always'+3.140000; -3.140000'>>> '{: f}; {: f}'.format(3.14, -3.14) # show a space for positive numbers' 3.140000; -3.140000'>>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the minus -- same as '{:f}; {:f}''3.140000; -3.140000'用%x和%o使用不同的类型输出值
>>> # format also supports binary numbers>>> "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'使用逗号作为数字千位分隔符
>>> '{:,}'.format(1234567890)'1,234,567,890'
将数字表示为百分数
>>> points = 19>>> total = 22>>> 'Correct answers: {:.2%}'.format(points/total)'Correct answers: 86.36%'
更复杂的例子
>>> for align, text in zip('<^>', ['left', 'center', 'right']):... '{0:{fill}{align}16}'.format(text, fill=align, align=align)...'left<<<<<<<<<<<<''^^^^^center^^^^^''>>>>>>>>>>>right'>>>>>> octets = [192, 168, 0, 1]>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)'C0A80001'>>> int(_, 16)3232235521>>>>>> width = 5>>> for num in range(5,12): ... for base in 'dXob':... print('{0:{width}{base}}'.format(num, base=base, width=width), end=' ')... print()... 5 5 5 101 6 6 6 110 7 7 7 111 8 8 10 1000 9 9 11 1001 10 A 12 1010 11 B 13 1011参考
https://docs.python.org/3/library/string.html
http://youngsterxyf.github.io/2013/01/26/python-string-format/
