how to convert bytes to string in Python 3

Question

I want to write a function that returns a string, not bytes.
the function:

def read_image(path):
    with open(path, "rb") as f:
        data = f.read()
    return data
image_data = read_image("/home/user/icon.jpg")

How to convert the value image_data to type str. If convert to string successfully, how to reconvert the string to bytes.

So why can't you just apply `str()` to whatever you want to return? — dmitryro, Jan 01 '18 at 04:11
@Primusa,.decode("utf-8") throw exception.```UnicodeDecodeError:'utf-8' codec can't decode byte 0xff``` — user3410960, Jan 01 '18 at 04:25
I don't think you can make a string out of a jpg image. What are you planning on doing with it? — Patrick Haugh, Jan 01 '18 at 04:31
In order to adapte Python 2. Some libs use my function, but the libs writen with Python 2.@PatrickHaugh — user3410960, Jan 01 '18 at 04:48
Why is this flagged as a duplicate? These two questions aren't the same, you can't decode an image's bytes. — Asriel, Jun 15 '20 at 19:20

MultiSkill · Answer 1 · 2018-01-01T06:13:23.633

In order to be compatible with older code you want to return a string object the way it was back in python2 and convert a bytes object to a string object.

There might be an easier way, but I'm not aware of one, so I would opt to do this:

return "".join( chr(x) for x in data)

Because iterating bytes results in integers, I'm forcibly converting them back to characters and joining the resulting array into a string.

In case you need to make the code portable so that your new method still works in Python2 as well as in Python 3 (albeit might be slower):

return "".join( chr(x) for x in bytearray(data) )

Bytearray itterates to integers in both py2 and py3, unlike bytes.

Hope that helps.

Wrong approach:

return data.decode(encoding="ascii", errors="ignore")

There might be ways to register a custom error handler, but as it is by default you are going to be missing any bytes that are outside the ascii range. Likewise using the UTF-8 encoding will mess your binary content.

Wrong approach 2

str(b'one') == "b'one'" #for py3, but "one" for py2

Consider base64 encoding instead of mapping chars – Agost Biro Dec 09 '19 at 10:51 — Agost Biro, Dec 09 '19 at 10:51
Or: `return "".join(map(chr,data))` – RufusVS Feb 05 '20 at 16:47 — RufusVS, Feb 05 '20 at 16:47

how to convert bytes to string in Python 3

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