创建流以在Python中从字符串迭代 [英] creating stream to iterate over from string in Python

问题描述

我想从Python中的字符串创建一个流，这样就相当于读取字符串，就像从文本文件中读取一样。类似于：

I want to create a stream from a string in Python so that it's equivalent to reading the string as if it's read from a text file. something like:

for line in open('myfile.txt'): print line

除了'myfile.txt'的内容存储在字符串 s 中。这是正确/最好的方法吗？

except the contents of 'myfile.txt' are stored in a string s. Is this the correct/best way to do it?

s = StringIO.StringIO("a\t\b\nc\td\n")
for line in s: print line

推荐答案

我想用Python中的字符串创建一个流，这样就相当于读取字符串，就像从文本文件中读取一样。

I want to create a stream from a string in Python so that it's equivalent to reading the string as if it's read from a text file.

是的，除非你真的这样做希望它在一个列表中。

Yes, unless you really do want it in a list.

如果打算逐行消费，你的方式是有意义的。

If it is intended to be consumed line by line, the way you are doing it makes sense.

StringIO（）创建一个类似文件的对象。

StringIO() creates a file-like object.

文件对象有一个方法， .readlines（），它将对象表示为一个列表。而不是实现列表中的数据，你可以迭代它，这是更多的内存光：

File objects have a method, .readlines(), which materialize the object as a list. Instead of materializing the data in a list, you can iterate over it, which is more memory light:

# from StringIO import StringIO # Python 2 import
from io import StringIO # Python 3 import

txt = "foo\nbar\nbaz"

这里我们将每行附加到列表中，以便我们可以演示迭代文件类对象并保持数据句柄。 （效率更高的是 list（file_like_io）。

Here we append each line into a list, so that we can demonstrate iterating over the file-like object and keeping a handle on the data. (More efficient would be list(file_like_io).

m_1 = []
file_like_io = StringIO(txt)
for line in file_like_io:
    m_1.append(line)

现在：

>>> m_1
['foo\n', 'bar\n', 'baz']

你可以退回你的io使用搜索任何索引点：

you can return your io to any index point with seek:

>>> file_like_io.seek(0)
>>> file_like_io.tell() #print where we are in the object now
0

如果你真的想要它在列表中

.readlines（）具体化了 StringIO 迭代器，好像有人做了 list（io） - 这被认为不太可取。

If you really want it in a list

.readlines() materializes the StringIO iterator as if one did list(io) - this is considered less preferable.

>>> m_2 = file_like_io.readlines() 

我们可以看到我们的结果是一样的：

And we can see that our results are the same:

>>> m_1==m_2
True

请记住，它是在换行符后拆分，保留在换行符中文本也是如此，因此您将为每个打印行获得两个换行符，打印时为双倍行距。

Keep in mind that it is splitting after the newlines, preserving them in the text as well, so you'll get two newlines for every printed line, double-spacing on print.

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