If I have a binary string, let say str = "010100011010101001001101100101100110101" which is an encoded by base64 version of some other string how can I decode this string?
It would have been great if your example string is actually something meaningful rather than something made up which makes this question rather unclear, but I will try my best here to figure out what you might have meant in the most verbose manner possible.
Assuming your actual input is a str that looks like this:
s = '101100101010011010000100011000001011010010110000100111000110000'
You can get the hexadecimal form of this by casting it to int using the base keyword argument
>>> i = int(s, base=2) # 6436561067884170800
Then turn it back into a string by formatting it like so:
>>> h = '%x' % i # '595342305a584e30'
Then use the binascii.a2b_hex function on the hexadecimal string to get the raw bytes:
>>> b64 = binascii.a2b_hex(h) # b'YSB0ZXN0'
If it is some valid base 64 encoded stream of bytes, you may then use base64.b64decode on that to get the actual bytes
>>> r = base64.b64decode(b64) # b'a test'
To turn that into a string, apply the correct codec to it (i.e. use bytes.encode).
Finally, if you cared to know how I generated that input, this is all the above, reversed into a single one-line function:
>>> '{0:b}'.format(int(binascii.b2a_hex(base64.b64encode(b'a test')), base=16))
'101100101010011010000100011000001011010010110000100111000110000'
Related
I have some text encoded to bytes using utf-8 encoding. When processing this text I incautiously used str() to make it a Unicode string because I assumed this would automatically decode the bytes object with the right encoding. This, however, is not the case. For example:
a = "عجائب"
a_bytes = a.encode(encoding="utf-8")
b = str(a_bytes)
yields
b = "b'\\xd8\\xb9\\xd8\\xac\\xd8\\xa7\\xd8\\xa6\\xd8\\xa8'"
which is not what I expected.
According to the docs
If neither encoding nor errors is given, str(object) returns type(object).__str__(object), [...].
So my question is: What is the implemented string representation of a bytes object in Python and can I recreate my original Unicode string from it in general?
It gives you a string containing the string representation of a bytes object:
>>> a = "عجائب"
>>> a_bytes = a.encode(encoding="utf-8")
>>> a_bytes
b'\xd8\xb9\xd8\xac\xd8\xa7\xd8\xa6\xd8\xa8'
>>> str(a_bytes)
"b'\\xd8\\xb9\\xd8\\xac\\xd8\\xa7\\xd8\\xa6\\xd8\\xa8'"
Meaning, you have a valid literal representing a bytes. You can parse that literal again to an actual bytes using ast.literal_eval:
>>> import ast
>>> ast.literal_eval(str(a_bytes))
b'\xd8\xb9\xd8\xac\xd8\xa7\xd8\xa6\xd8\xa8'
This is again the same as a_bytes. You can properly decode those to a str again, either using .decode, or by using the encoding parameter of str:
>>> str(a_bytes, 'utf-8')
'عجائب'
>>> a_bytes.decode('utf-8')
'عجائب'
When you call str() and pass it as an argument a bytes variable, it converts from bytes to string. If you want to decode from utf-8 bytes to the original string, you need to use decode() function and specify the initial coding method:
a = "عجائب"
a_bytes = a.encode(encoding="utf-8")
b = str(a_bytes)
print(b)
print(a_bytes)
print(a_bytes.decode("utf-8")) #Prints decoded string from bytes
Output:
b'\xd8\xb9\xd8\xac\xd8\xa7\xd8\xa6\xd8\xa8'
b'\xd8\xb9\xd8\xac\xd8\xa7\xd8\xa6\xd8\xa8'
عجائب
I need to send a string via tcp. One of the first sections of the string is the length of the command variable
Example:
command = STATUS?UPDATE
I need to send the following string below
sendCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'+command+'\x0D\x0A'
My string length is 11 so I need STRINGLENGTH to be the hex equivalent of 11, which is 0xB, except that I need it to output as \x0B
Padding it with the leading 0 is easy, but I cannot get it to output as \x instead of 0x, and if I do a string replace it is treated as text and not as hex, so it doesn't work.
My final hex string should be:
\x00\x00\x00\x0B\x02\x53\x54\x41\x54\x55\x53\x3f\x55\x53\x45\x52\x0D\x0A
I am instead getting:
\x00\x00\x000x0B\x02\x53\x54\x41\x54\x55\x53\x3f\x55\x53\x45\x52\x0D\x0A
Any ideas on how to format it correctly?
So, this is a bit of a round-about fashion, but use a bytes object:
>>> STRINGLENGTH = bytes([11]).decode()
>>> endCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'
>>> endCommand
'\x00\x00\x00\x0b\x02'
Almost certainly, you are going to want to change your str object back to a bytes object, but the above should get you going.
I suspect what you were doing was using the hex function:
>>> STRINGLENGTH = hex(11)
>>> endCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'
>>> endCommand
'\x00\x00\x000xb\x02'
The fundamental thing you need to understand is that you aren't working with "hex", you are working with bytes. Hex is just how bytes are traditionally represented. The hex helper function returns a hexadecimal representation, as a string of an integer. But that isn't what you want. You want the byte corresponding to the value 11.
Note, for the ascii-range, chr(i) might works as well, so
>>> STRINGLENGTH = chr(11)
>>> endCommand = '\x00\x00\x00'+STRINGLENGTH+'\x02'
>>> endCommand
'\x00\x00\x00\x0b\x02'
But be careful, say you wanted the number 129, you have to care about the encoding...
>>> chr(129)
'\x81'
But in bytes, in UTF-8, that's actually represented by two different bytes
>>> chr(129).encode()
b'\xc2\x81'
>>> list(chr(129).encode())
[194, 129]
Which of course, depends on the encoding:
>>> chr(129).encode('latin')
b'\x81'
>>> list(chr(129).encode('latin'))
[129]
>>>
For that reason, I think it is safer to stick with the slightly wordier:
>>> bytes([129])
b'\x81'
I should not expect any error here. I just want to take the string literaly and translate it into its bytes. I don't want to encode or decode anything.
I am taking here a stupid example:
>>> astring
u'\xb0'
Stupid enough to give me headache...
>>> bytes(astring)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xb0' in position...
One horrible trick is to do this:
>>> bytes(repr(astring)[2:-1])
'\xb0'
One other bad solution is:
>>> bytes(astring.encode("utf-8"))
'\xc2\xb0'
It is a bad solution because my string is not composed of two chars. This is wrong.
Another awful solution would be:
>>> bytes(''.join(map(bytes, [chr(ord(c)) for c in astring])))
'\xb0'
I am using Python 2.7
Background
I would like to compare two columns on a database where the encoding is unknown and sometime conflicting. I don't care about wrong chars on my dump. I just want to get it to have a look at it.
If your Unicode strings are guaranteed to only contain codepoints < 256 then you can convert them to bytes using the Latin1 encoding. Here's some Python 2 code that performs this conversion on all codepoints in range(256).
r = range(256)
s = u''.join([unichr(i) for i in r])
print repr(s)
b = s.encode('latin1')
print repr(b)
a = [ord(c) for c in b]
print a == r
output
u'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
True
FWIW, here's the equivalent Python 3 code.
r = range(256)
s = u''.join([chr(i) for i in r])
print(repr(s))
b = s.encode('latin1')
print(repr(b))
print(list(b) == list(r))
output
'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0¡¢£¤¥¦§¨©ª«¬\xad®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ'
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
True
Note that the Python 3 Unicode repr output is a little more human-friendly.
You cannot just 'take the string literally' because the actual, internal, bytes representation of your string is not fixed and is an implementation detail of the your python interpreter that your should not rely on (see PEP3993, on the same system different string can use different internal encoding).
That also means that to get a byte representation of you string, you really need to encode it, and thus specify the encoding.
By the way, astring.encode("utf-8") is not wrong (and already returns a bytes, you don't need the extra bytes(...) in your code), as in utf-8 a single character can be represented as several bytes.
You should be able to just add b before the quotes of the string.
>>> astring = b'\xb0'
>>> astring
b'\xb0'
>>> bytes(astring)
b'\xb0'
>>>
Putting b before the string makes it a bytes object. No more UnicodeEncodeError.
I want to encode string to bytes.
To convert to byes, I used byte.fromhex()
>>> byte.fromhex('7403073845')
b't\x03\x078E'
But it displayed some characters.
How can it be displayed as hex like following?
b't\x03\x078E' => '\x74\x03\x07\x38\x45'
I want to encode string to bytes.
bytes.fromhex() already transforms your hex string into bytes. Don't confuse an object and its text representation -- REPL uses sys.displayhook that uses repr() to display bytes in ascii printable range as the corresponding characters but it doesn't affect the value in any way:
>>> b't' == b'\x74'
True
Print bytes to hex
To convert bytes back into a hex string, you could use bytes.hex method since Python 3.5:
>>> b't\x03\x078E'.hex()
'7403073845'
On older Python version you could use binascii.hexlify():
>>> import binascii
>>> binascii.hexlify(b't\x03\x078E').decode('ascii')
'7403073845'
How can it be displayed as hex like following? b't\x03\x078E' => '\x74\x03\x07\x38\x45'
>>> print(''.join(['\\x%02x' % b for b in b't\x03\x078E']))
\x74\x03\x07\x38\x45
The Python repr can't be changed. If you want to do something like this, you'd need to do it yourself; bytes objects are trying to minimize spew, not format output for you.
If you want to print it like that, you can do:
from itertools import repeat
hexstring = '7403073845'
# Makes the individual \x## strings using iter reuse trick to pair up
# hex characters, and prefixing with \x as it goes
escapecodes = map(''.join, zip(repeat(r'\x'), *[iter(hexstring)]*2))
# Print them all with quotes around them (or omit the quotes, your choice)
print("'", *escapecodes, "'", sep='')
Output is exactly as you requested:
'\x74\x03\x07\x38\x45'
i want to convert the chinese character to the unicode format, like '\uXXXX'
but when i use str.encode('utf-16be'), it'll show that:
b'\xOO\xOO'
so, i write some code to perform my request as below:
data="index=索引?"
print(data.encode('UTF-16LE'))
def convert(s):
returnCode=[]
temp=''
for n in s.encode('utf-16be'):
if temp=='':
if str.replace(hex(n),'0x','')=='0':
temp='00'
continue
temp+=str.replace(hex(n),'0x','')
else:
returnCode.append(temp+str.replace(hex(n),'0x',''))
temp=''
return returnCode
print(convert(data))
can someone give me suggestions to do this conversion in python 3.x?
I'm not sure if I understand you well.
Unicode is like a type. In python 3, all strings are unicode, so when you write data = "index=索引?" then data is already unicode. If you want to get an alternative representation just for displaying, you could use:
def display_unicode(data):
return "".join(["\\u%s" % hex(ord(l))[2:].zfill(4) for l in data])
>>> data = "index=索引?"
>>> print(display_unicode(data))
\u0069\u006e\u0064\u0065\u0078\u003d\u7d22\u5f15\u003f
Note that the string has now real backslashes and numeric representations, not unicode characters.
But there may be other alternatives
>>> data.encode('ascii', 'backslashreplace')
b'index=\\u7d22\\u5f15?'
>>> data.encode('unicode_escape')
b'index=\\u7d22\\u5f15?'
Try to decode first, like: s.decode('utf-8').encode('utf-16be')?