Convert bytes to a string

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I captured the standard output of an external program into a bytes object:

>>> from subprocess import *
>>> command_stdout = Popen(['ls', '-l'], stdout=PIPE).communicate()[0]
>>>
>>> command_stdout
b'total 0\n-rw-rw-r-- 1 thomas thomas 0 Mar  3 07:03 file1\n-rw-rw-r-- 1 thomas thomas 0 Mar  3 07:03 file2\n'

I want to convert that to a normal Python string, so that I can print it like this:

>>> print(command_stdout)
-rw-rw-r-- 1 thomas thomas 0 Mar  3 07:03 file1
-rw-rw-r-- 1 thomas thomas 0 Mar  3 07:03 file2

I tried the binascii.b2a_qp() method, but got the same bytes object again:

>>> binascii.b2a_qp(command_stdout)
b'total 0\n-rw-rw-r-- 1 thomas thomas 0 Mar  3 07:03 file1\n-rw-rw-r-- 1 thomas thomas 0 Mar  3 07:03 file2\n'

How do I convert the bytes object to a str with Python 3?

24 Answers

Decode the bytes object to produce a string:

>>> b"abcde".decode("utf-8") 
'abcde'

The above example assumes that the bytes object is in UTF-8, because it is a common encoding. However, you should use the encoding your data is actually in!

Decode the byte string and turn it in to a character (Unicode) string.


Python 3:

encoding = 'utf-8'
b'hello'.decode(encoding)

or

str(b'hello', encoding)

Python 2:

encoding = 'utf-8'
'hello'.decode(encoding)

or

unicode('hello', encoding)

Since this question is actually asking about subprocess output, you have more direct approaches available. The most modern would be using subprocess.check_output and passing text=True (Python 3.7+) to automatically decode stdout using the system default coding:

text = subprocess.check_output(["ls", "-l"], text=True)

For Python 3.6, Popen accepts an encoding keyword:

>>> from subprocess import Popen, PIPE
>>> text = Popen(['ls', '-l'], stdout=PIPE, encoding='utf-8').communicate()[0]
>>> type(text)
str
>>> print(text)
total 0
-rw-r--r-- 1 wim badger 0 May 31 12:45 some_file.txt

The general answer to the question in the title, if you're not dealing with subprocess output, is to decode bytes to text:

>>> b'abcde'.decode()
'abcde'

With no argument, sys.getdefaultencoding() will be used. If your data is not sys.getdefaultencoding(), then you must specify the encoding explicitly in the decode call:

>>> b'caf\xe9'.decode('cp1250')
'café'

If you should get the following by trying decode():

AttributeError: 'str' object has no attribute 'decode'

You can also specify the encoding type straight in a cast:

>>> my_byte_str
b'Hello World'

>>> str(my_byte_str, 'utf-8')
'Hello World'

If you have had this error:

utf-8 codec can't decode byte 0x8a,

then it is better to use the following code to convert bytes to a string:

bytes = b"abcdefg"
string = bytes.decode("utf-8", "ignore") 

Bytes

m=b'This is bytes'

Converting to string

Method 1

m.decode("utf-8")

or

m.decode()

Method 2

import codecs
codecs.decode(m,encoding="utf-8")

or

import codecs
codecs.decode(m)

Method 3

str(m,encoding="utf-8")

or

str(m)[2:-1]

Result

'This is bytes'

For your specific case of "run a shell command and get its output as text instead of bytes", on Python 3.7, you should use subprocess.run and pass in text=True (as well as capture_output=True to capture the output)

command_result = subprocess.run(["ls", "-l"], capture_output=True, text=True)
command_result.stdout  # is a `str` containing your program's stdout

text used to be called universal_newlines, and was changed (well, aliased) in Python 3.7. If you want to support Python versions before 3.7, pass in universal_newlines=True instead of text=True

We can decode the bytes object to produce a string using bytes.decode(encoding='utf-8', errors='strict'). For documentation see bytes.decode.

Python 3 example:

byte_value = b"abcde"
print("Initial value = {}".format(byte_value))
print("Initial value type = {}".format(type(byte_value)))
string_value = byte_value.decode("utf-8")
# utf-8 is used here because it is a very common encoding, but you need to use the encoding your data is actually in.
print("------------")
print("Converted value = {}".format(string_value))
print("Converted value type = {}".format(type(string_value)))

Output:

Initial value = b'abcde'
Initial value type = <class 'bytes'>
------------
Converted value = abcde
Converted value type = <class 'str'>

Note: In Python 3, by default the encoding type is UTF-8. So, <byte_string>.decode("utf-8") can be also written as <byte_string>.decode()

Decode with .decode(). This will decode the string. Pass in 'utf-8') as the value in the inside.

def toString(string):    
    try:
        return v.decode("utf-8")
    except ValueError:
        return string

b = b'97.080.500'
s = '97.080.500'
print(toString(b))
print(toString(s))

If you want to convert any bytes, not just string converted to bytes:

with open("bytesfile", "rb") as infile:
    str = base64.b85encode(imageFile.read())

with open("bytesfile", "rb") as infile:
    str2 = json.dumps(list(infile.read()))

This is not very efficient, however. It will turn a 2 MB picture into 9 MB.

Try this:

bytes.fromhex('c3a9').decode('utf-8') 

Try using this one; this function will ignore all the non-character sets (like UTF-8) binaries and return a clean string. It is tested for Python 3.6 and above.

def bin2str(text, encoding = 'utf-8'):
    """Converts a binary to Unicode string by removing all non Unicode char
    text: binary string to work on
    encoding: output encoding *utf-8"""

    return text.decode(encoding, 'ignore')

Here, the function will take the binary and decode it (converts binary data to characters using the Python predefined character set and the ignore argument ignores all non-character set data from your binary and finally returns your desired string value.

If you are not sure about the encoding, use sys.getdefaultencoding() to get the default encoding of your device.

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