How to wrap binary streams with TextIOWrapper for Python 2/3?

General Discussions
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1

How can I wrap an open binary stream – a Python 2 file, a Python 3 io.BufferedReader, or an io.BytesIO – in a python textiowrapper?

I’m trying to write code that works unchanged:

  • On Python 2.
  • On Python 3.
  • With binary streams generated from the standard library (i.e., I can’t control the type).
  • With binary streams made to be test doubles (i.e., no file handle, can’t re-open).

The goal is to produce an io.TextIOWrapper that wraps the specified stream, as its API is expected by other parts of the standard library. While other file-like types exist, they don’t provide the correct API.

How can I write code that works for both Python 2 and Python 3, with both the test doubles and the real objects, to wrap an io.TextIOWrapper around the already-open byte stream?

2

Well, I’ve worked a lot with python textiowrapper across different Python versions. In Python 3, it’s pretty straightforward—io.TextIOWrapper is the go-to tool. But in Python 2, you don’t have TextIOWrapper, so you’ll need to use codecs.open instead. Here’s how you can handle it:

import io
import codecs
import sys

def wrap_stream(binary_stream):
    if sys.version_info[0] >= 3:
        # Python 3: Directly use python textiowrapper
        return io.TextIOWrapper(binary_stream, encoding='utf-8')
    else:
        # Python 2: Use codecs.getreader to simulate the behavior
        return codecs.getreader('utf-8')(binary_stream)

In this solution:

  • For Python 3, io.TextIOWrapper does all the work, wrapping the binary stream.
  • For Python 2, I used codecs.getreader to wrap the stream similarly, which mimics the Python 3 behavior.
3

Good point, @shashank_watak! Adding to that, it’s often handy to check if the stream is a specific type, like BufferedReader or BytesIO. This can give you more control over the stream you’re working with. Here’s a refined approach that works for both Python versions:

import io
import sys

def wrap_stream(binary_stream):
    if isinstance(binary_stream, io.BufferedReader) or isinstance(binary_stream, io.BytesIO):
        if sys.version_info[0] >= 3:
            # Python 3: Use python textiowrapper directly
            return io.TextIOWrapper(binary_stream, encoding='utf-8')
        else:
            # Python 2: Use codecs.getreader for the same effect
            return codecs.getreader('utf-8')(binary_stream)
    else:
        raise TypeError("Unsupported stream type")

This solution ensures you’re dealing with only valid stream types (BufferedReader or BytesIO). If you have other stream types, you can raise an error to handle that separately. It’s a little more robust than just blindly wrapping the stream, which can be helpful for debugging.

4

That’s a nice addition, @alveera.khn! And to build on that, I’ve worked with python textiowrapper quite a bit, especially when handling BytesIO streams. If you know you’re always working with BytesIO, you can simplify things quite a bit. Here’s a solution that ensures compatibility for both Python 2 and 3:

import io
import sys

def wrap_stream(binary_stream):
    if sys.version_info[0] >= 3:
        # Python 3: Directly wrap with python textiowrapper
        return io.TextIOWrapper(binary_stream, encoding='utf-8')
    else:
        # Python 2: Wrap using io.BytesIO with utf-8 encoding
        return io.TextIOWrapper(binary_stream, encoding='utf-8')

This assumes your binary_stream is already an instance of BytesIO, and it should work across both Python versions. The key here is that you’re still using TextIOWrapper in Python 3, and the fallback is just a TextIOWrapper on the Python 2 side—since Python 2 doesn’t have the exact equivalent of TextIOWrapper, it’s a way of ensuring consistent behavior regardless of the version you’re using.