如何在Python中用零填充数字字符串？
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How to pad a numeric string with zeros to the right in Python?
提问by yucer
Python strings have a method called zfillthat allows to pad a numeric string with zeros to the left.
Python 字符串有一个方法zfill，它允许在数字字符串的左边填充零。
In : str(190).zfill(8)
Out: '00000190'
How can I make the pad to be on the right ?
我怎样才能让垫子在右边？
回答by NarūnasK
See Format Specification Mini-Language:
请参阅格式规范迷你语言：
In [1]: '{:<08d}'.format(190)
Out[1]: '19000000'
In [2]: '{:>08d}'.format(190)
Out[2]: '00000190'
回答by Manoel Vilela
As maybe a alternative more portable [1] and efficient [2], actually you can just use str.ljust.
作为更便携 [1] 和高效 [2] 的替代方案，实际上您可以只使用str.ljust。
In [2]: '190'.ljust(8, '0')
Out[2]: '19000000'
In [3]: str.ljust?
Docstring:
S.ljust(width[, fillchar]) -> str
Return S left-justified in a Unicode string of length width. Padding is
done using the specified fill character (default is a space).
Type: method_descriptor
[1] format is not present on old python versions. format specifier was added since Python 3.0 (see PEP 3101) and Python 2.6.
[1] 格式在旧的 python 版本中不存在。自 Python 3.0（参见PEP 3101）和 Python 2.6起添加了格式说明符。
[2] reverse twice is an expensive operation.
[2] 反转两次是一项昂贵的操作。
回答by yucer
Hint: The string can be inverted twice: before and after using the zfillmethod:
提示：字符串可以反转两次：使用zfill方法之前和之后：
In : acc = '991000'
In : acc[::-1].zfill(9)[::-1]
Out: '991000000'
Or even more easier:
或者更简单：
In : acc.ljust(9, '0')
Out: '991000000'
