您不能更改 "".format() 因为它是内置的，但如果提供字符串和方法的参数:

You cannot change "".format() as it is a built-in but if it is acceptable to provide the string and parameters to a method:

print(kf.format("{:t{}}  {}", key, ':', value))

您可以通过子类化 string.Formatter 以允许空格式字段并提供特殊类型处理程序 t 来实现:

you can do so by subclassing string.Formatter to allow empty format fields and provide a special type handler t:

from string import Formatter
import sys

if sys.version_info < (3,):
    int_type = (int, long)
else:
    int_type = (int)

class TrailingFormatter(Formatter):

    def vformat(self, *args):
        self._automatic = None
        return super(TrailingFormatter, self).vformat(*args)

    def get_value(self, key, args, kwargs):
        if key == '':
            if self._automatic is None:
                self._automatic = 0
            elif self._automatic == -1:
                raise ValueError("cannot switch from manual field specification "
                                 "to automatic field numbering")
            key = self._automatic
            self._automatic += 1
        elif isinstance(key, int_type):
            if self._automatic is None:
                self._automatic = -1
            elif self._automatic != -1:
                raise ValueError("cannot switch from automatic field numbering "
                                 "to manual field specification")
        return super(TrailingFormatter, self).get_value(key, args, kwargs)

    def format_field(self, value, spec):
        if len(spec) > 1 and spec[0] == 't':
            value = str(value) + spec[1]  # append the extra character
            spec = spec[2:]
        return super(TrailingFormatter, self).format_field(value, spec)

kf = TrailingFormatter()
w = 20
ch = ':'
x = dict(a_key=23, another_key=42)

for k in sorted(x):
    v = x[k]
    print(kf.format('{:t{}<{}} {}', k, ch, w, v))

给你:

 a_key:               23
 another_key:         42

您当然可以对 ch 和 w 值进行硬编码:

You can of course hardcode the ch, and w values:

    print(kf.format('{:t:<20} {}', k, v))

可读性更好，但灵活性较差.

for better readability, but less flexibility.

Python 3.4 string.Formatter() 的后向移植，其中包括(至少)高达 3.5.0rc1 的版本的错误修复，其中包括此代码现在可在 PyPI

A backport of the Python 3.4 string.Formatter() that includes a bugfix for versions (at least) up to 3.5.0rc1, that includes this code is now available on PyPI