不需要正则表达式，但您确实希望在接受的答案中使用字符串格式而不是字符串连接。

这可能是将字符串数据截断为75个字符的最规范的python方法。

>>> data = "saddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsaddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsadddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd"
>>> info = "{}..".format(data[:75]) if len(data) > 75 else data
>>> info
'111111111122222222223333333333444444444455555555556666666666777777777788888...'

这是另一种解决方案。在测试结束时，你会得到一些关于测试的反馈。

data = {True: data[:75] + '..', False: data}[len(data) > 75]

       >>> info = lambda data: len(data)>10 and data[:10]+'...' or data
       >>> info('sdfsdfsdfsdfsdfsdfsdfsdfsdfsdfsdf')
           'sdfsdfsdfs...'
       >>> info('sdfsdf')
           'sdfsdf'
       >>> 

假设string是我们希望截断的字符串，而nchars是输出字符串中所需的字符数。

stryng = "sadddddddddddddddddddddddddddddddddddddddddddddddddd"
nchars = 10

我们可以像下面这样截断字符串:

def truncate(stryng:str, nchars:int):
    return (stryng[:nchars - 6] + " [...]")[:min(len(stryng), nchars)]

某些测试用例的结果如下所示:

s = "sadddddddddddddddddddddddddddddd!"
s = "sa" + 30*"d" + "!"

truncate(s, 2)                ==  sa
truncate(s, 4)                ==  sadd
truncate(s, 10)               ==  sadd [...]
truncate(s, len(s)//2)        ==  sadddddddd [...]

我的解决方案为上面的测试用例产生了合理的结果。

但一些病理病例如下:

一些病理病例!

truncate(s, len(s) - 3)()       ==  sadddddddddddddddddddddd [...]
truncate(s, len(s) - 2)()       ==  saddddddddddddddddddddddd [...]
truncate(s, len(s) - 1)()       ==  sadddddddddddddddddddddddd [...]
truncate(s, len(s) + 0)()       ==  saddddddddddddddddddddddddd [...]
truncate(s, len(s) + 1)()       ==  sadddddddddddddddddddddddddd [...
truncate(s, len(s) + 2)()       ==  saddddddddddddddddddddddddddd [..
truncate(s, len(s) + 3)()       ==  sadddddddddddddddddddddddddddd [.
truncate(s, len(s) + 4)()       ==  saddddddddddddddddddddddddddddd [
truncate(s, len(s) + 5)()       ==  sadddddddddddddddddddddddddddddd 
truncate(s, len(s) + 6)()       ==  sadddddddddddddddddddddddddddddd!
truncate(s, len(s) + 7)()       ==  sadddddddddddddddddddddddddddddd!
truncate(s, 9999)()             ==  sadddddddddddddddddddddddddddddd!

值得注意的是,

当字符串包含换行字符(\n)时，可能会出现问题。 当nchars > len(s)时，我们应该打印字符串s，而不是试图打印“[…]”

下面是更多的代码:

import io

class truncate:
    """
        Example of Code Which Uses truncate:
        ```
            s = "\r<class\n 'builtin_function_or_method'>"
            s = truncate(s, 10)()
            print(s)
                    ```
                Examples of Inputs and Outputs:
                        truncate(s, 2)()   ==  \r
                        truncate(s, 4)()   ==  \r<c
                        truncate(s, 10)()  ==  \r<c [...]
                        truncate(s, 20)()  ==  \r<class\n 'bu [...]
                        truncate(s, 999)() ==  \r<class\n 'builtin_function_or_method'>
                    ```
                Other Notes:
                    Returns a modified copy of string input
                    Does not modify the original string
            """
    def __init__(self, x_stryng: str, x_nchars: int) -> str:
        """
        This initializer mostly exists to sanitize function inputs
        """
        try:
            stryng = repr("".join(str(ch) for ch in x_stryng))[1:-1]
            nchars = int(str(x_nchars))
        except BaseException as exc:
            invalid_stryng =  str(x_stryng)
            invalid_stryng_truncated = repr(type(self)(invalid_stryng, 20)())

            invalid_x_nchars = str(x_nchars)
            invalid_x_nchars_truncated = repr(type(self)(invalid_x_nchars, 20)())

            strm = io.StringIO()
            print("Invalid Function Inputs", file=strm)
            print(type(self).__name__, "(",
                  invalid_stryng_truncated,
                  ", ",
                  invalid_x_nchars_truncated, ")", sep="", file=strm)
            msg = strm.getvalue()

            raise ValueError(msg) from None

        self._stryng = stryng
        self._nchars = nchars

    def __call__(self) -> str:
        stryng = self._stryng
        nchars = self._nchars
        return (stryng[:nchars - 6] + " [...]")[:min(len(stryng), nchars)]

下面是一个简单的函数，它将从任意一侧截断给定字符串:

def truncate(string, length=75, beginning=True, insert='..'):
    '''Shorten the given string to the given length.
    An ellipsis will be added to the section trimmed.

    :Parameters:
        length (int) = The maximum allowed length before trunicating.
        beginning (bool) = Trim starting chars, else; ending.
        insert (str) = Chars to add at the trimmed area. (default: ellipsis)

    :Return:
        (str)

    ex. call: truncate('12345678', 4)
        returns: '..5678'
    '''
    if len(string)>length:
        if beginning: #trim starting chars.
            string = insert+string[-length:]
        else: #trim ending chars.
            string = string[:length]+insert
    return string

更简短的是:

info = data[:75] + (data[75:] and '..')