如何使用python [duplicate]限制文本文件中每行的长度

Question

这个问题在这里已有答案：

• set a limit to the number of words or characters in a string 3回答

我有一个以下类型的文本文件 -

eng Firstly, in the course of the last few decades the national 
 eng Secondly, the national courts will be empowered to implement
 eng However, I am convinced of the fact that the White Paper has put us on 
 the right path.

我想限制每行的长度（比方说）9个单词。我尝试使用python的read_line方法，但它只指定了行的大小。我无法找到任何其他合适的方法。怎么做 ？

样品输出 -

eng Firstly, in the course of the last few
eng Secondly, the national courts will be empowered to
eng However, I am convinced of the fact that 

Answer 1

要将字符串的前n个单词作为字符串：

def first_n_words(s, n):
    return ' '.join(s.split()[:n])

Answer 2

您可以像这样列出每个单词：

with open(file, 'r') as f:
    lines = []
    for line in f:
        lines.append(line.rstrip('\n').split())

现在使用自动截断的切片将每一行限制为9：

with open(file, 'w') as f:
    for line in lines:
        f.write(' '.join(line[:9]))
        f.write('\n')