Question

我想用给定的字符串替换文本文件中的某段文本。例如，给定以下文件内容：

1
---From here---
2
---To here---
3

我想编写一个python函数，在以这种方式的格式启动时：

replaceSection('pathToFile','---From here---\n','---To here---\n','Woo Hoo!\n')

这应该将原始文件更改为：

1
Woo Hoo!
3

我已经提出了一个简单的实现（下面），但我认为它有一些缺点，我想知道是否有更简单的实现：

代码很长，这使得它的理解有点麻烦
我迭代代码两次（而不是inplace替换） - 这似乎效率低下

这与我在C ++代码中使用的实现相同，我猜Python有一些隐藏的优点可以使实现更加优雅

def replaceSection(pathToFile,sectionOpener,sectionCloser,replaceWith = ''):
    '''
    Delete all the lines in a certain section of the given file and put instead a customized text.

    Return:
    None if a replacement was performed and -1 otherwise.
    '''
    f = open(pathToFile,"r")
    lines = f.readlines()
    f.close()
    if sectionOpener in lines:
        isWrite = True # while we are outside the block and current line should be kept
        f = open(pathToFile,"w")
        #Write each line until reaching a section opener
        # from which write nothing until reaching the section end. 
        for line in lines :
            if line == sectionOpener:
                isWrite = False
            if isWrite:
            # We are outside the undesired section and hence want to keep current line    
                f.write(line)
            else:
                if line == sectionCloser:
                    # It's the last line of the section
                    f.write(replaceWith)
                    )
                    isWrite = True
                else:
                    # Current line is from the block we wish to delete
                    # so don't write it.
                    pass
        f.flush()
        f.close()
    else:
        return -1

Answer 1

在这里你可以找到你的2个模式的位置：这会划分文本的一部分，你只需要用你的新模式替换它：

>>> f = my_file.readlines()
>>> beg = f.index('---From here---')
>>> end = f.index('---To here---') + len('---To here---')
>>> print f.replace(f[beg:end], 'Woo woo !')
1
Woo woo !
3

请注意第二个分隔符的长度（因此f.index('---To here---') + len('---To here---')）。

Answer 2

这是基于itertools的方法：

from itertools import takewhile, dropwhile, chain, islice

with open('input') as fin, open('output', 'w') as fout:
    fout.writelines(chain(
        takewhile(lambda L: L != '---From here---\n', fin),
        ['Woo Hoo!\n'],
        islice(dropwhile(lambda L: L != '---To here---\n', fin), 1, None)
        )
    )

所以，在我们到达from标记之前，写出原始行，然后写出你想要的行，然后忽略所有内容直到结束标记，并写下剩下的行（跳过第一行，因为它会是结束标记）...

替换文件中的所有行[fromString，toString]

2 个答案: