Convert from '_io.BytesIO' to a bytes-like object in python3.6?

Question

I am using this function to uncompress the body or a HTTP response if it is compressed with gzip, compress or deflate.

def uncompress_body(self, compression_type, body):
    if compression_type == 'gzip' or compression_type == 'compress':
        return zlib.decompress(body)
    elif compression_type == 'deflate':
        compressor = zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS)
        compressed = compressor.compress(body)
        compressed += compressor.flush()
        return base64.b64encode(compressed)

    return body

However python throws this error message.

TypeError: a bytes-like object is required, not '_io.BytesIO'

on this line:

return zlib.decompress(body)

Essentially, how do I convert from '_io.BytesIO' to a bytes-like object?

score 45 · Accepted Answer · answered Jan 10 '19 at 22:28

45

It's a file-like object. Read them:

>>> b = io.BytesIO(b'hello')
>>> b.read()
b'hello'

If the data coming in from body is too large to read into memory, you'll want to refactor your code and use zlib.decompressobj instead of zlib.decompress.

answered Jan 10 '19 at 22:28

wim

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When you overthink a basic solution :D – Cyril N. Jan 07 '21 at 13:29

score 23 · Answer 2 · answered Sep 19 '19 at 07:46

In case you write into the object first, make sure to reset the stream before reading:

>>> b = io.BytesIO()
>>> image = PIL.Image.open(path_to_image)
>>> image.save(b, format='PNG')
>>> b.seek(0)
>>> b.read()
b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x06\xcf\x00\x00\x03W\x08\x02\x00'

or directly get the data with getvalue

>>> b.getvalue()
b'\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x06\xcf\x00\x00\x03W\x08\x02\x00'

Convert from '_io.BytesIO' to a bytes-like object in python3.6?

2 Answers2