替换流中的某些字符 [英] Replace certain characters in stream

问题描述

我有一个将输入流作为输入的方法(一个 .yml 解析器).问题是它在某些地方遇到某些字符时会抛出错误，例如%.

I have a method (a .yml parser) that takes an input stream as input. The problem is that it throws errors when it encounters certain characters in certain places e.g. %.

我想做的是获取流，用占位符替换所有 %，然后将其传递给解析器.

What I would like to do is take the stream, replace all of the % with a place holder, and then pass it to the parser.

这是我所拥有的(不适用于当前输入):

This is what I have (which doesn't work with the current input):

    stream = open('file.yml', 'r')
    dict = yaml.safe_load(stream)

但我认为我需要的是:

    stream = open('file.yml', 'r')
    temp_string = stringFromString(stream)     #convert stream to string
    temp_string.replace('%', '_PLACEHOLDER_')  #replace with place holder
    stream = streamFromString(temp_String)     #conver back to stream
    dict = yaml.safe_load(stream)

推荐答案

显然这里的原始答案不再有效，并且该库现在需要一个类似文件的对象.

Apparently the original answer here no longer appears to work, and the library now requires a file-like object.

鉴于此，它变得有点尴尬.您可以编写自己的包装器，以类似文件的方式起作用(其基础可能是 io.TextIOBase) 并在缓冲区中进行替换，但如果您愿意牺牲懒惰，最简单的解决方案大致是最初的问题中建议:在内存中进行替换.

Given that, it becomes a little more awkward. You could write your own wrapper that acts in a file-like way (the basis for this would probably be io.TextIOBase) and does the replacement in a buffer, but if you are willing to sacrifice laziness, the easiest solution is roughly what was originally suggested in the question: do the replacement in memory.

将字符串转换为类文件对象的解决方案是 io.StringIO.

The solution for turning a string into a file-like object is io.StringIO.

旧答案:

这样做的一个好方法是编写一个生成器，这样它就可以保持惰性(不需要一次读入整个文件):

A good way of doing this would be to write a generator, that way it remains lazy (the whole file doesn't need to be read in at once):

def replace_iter(iterable, search, replace):
    for value in iterable:
        value.replace(search, replace)
        yield value

with open("file.yml", "r") as file:
    iterable = replace_iter(file, "%", "_PLACEHOLDER")
    dictionary = yaml.safe_load(iterable)

注意使用 with 语句打开文件 - 这是在 Python 中打开文件的最佳方式，因为它确保文件被正确关闭，即使发生异常.

Note the use of the with statement to open the file - this is the best way to open files in Python, as it ensures files get closed properly, even when exceptions occur.

另请注意，dict 是一个糟糕的变量名，因为它会破坏内置的 dict() 并阻止您使用它.

Also note that dict is a poor variable name, as it will smash the built in dict() and stop you from using it.

请注意，您的 stringFromStream() 函数本质上是 file.read()，而 steamFromString() 是 data.splitlines().您所说的流"实际上只是字符串(文件行)上的迭代器.

Do note that your stringFromStream() function is essentially file.read(), and steamFromString() is data.splitlines(). What you are calling a 'stream' is actually just an iterator over strings (the lines of the file).

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