python中的字符串格式化是什么？

Question

谢谢！

python中的字符串格式化是什么？为什么要做呢？
python中的字符串格式化是什么？为什么要做呢？

Answer 1

执行字符串格式化操作。调用此方法的字符串可以包含字符串字面值或者以花括号 {} 括起来的替
换域。每个替换域可以包含一个位置参数的数字索引，或者一个关键字参数的名称。返回的字符串
副本中每个替换域都会被替换为对应参数的字符串值。
>>> "The sum of 1 + 2 is {0}".format(1+2)
'The sum of 1 + 2 is 3'

>>> '{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')
>>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad') # arguments' indices can be repeated
'abracadabra'
>>> '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:
>>> coord = (3, 5)
>>> 'X: {0[0]}; Y: {0[1]}'.format(coord)
'X: 3; Y: 5'
替代 %s 和 %r:
>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"
对齐文本以及指定宽度:
>>> '{:<30}'.format('left aligned')
'left aligned '
>>> '{:>30}'.format('right aligned')
' right aligned'
>>> '{:^30}'.format('centered')
' centered '
>>> '{:*^30}'.format('centered') # use '*' as a fill char