Python convert string to null terminated byte string

Question

I'm trying to convert a python string to a null terminated byte string. I don't need this string for use in my python program, but I need to have the string in this format and use this output somewhere else.

But basically, for example, I would like to convert the string "cat" to "\x63\x61\x74" if possible, in some way or another.

I wasn't able to find a suitable solution for this problem so far.

I have one possible solution, but I was wondering if there was a better way to do this. This just places the hex values in a list. Not in the exact format above, but similar outcome.

text = "asjknlkjsndfskjn"
hexlist = []

for i in range(0, len(str)):
    hexlist.append(hex(ord(str[i:i+1])))

print(hexlist)

So, just to get it right: for instance the second element of your new string would be x, am I right? — csabinho
– csabinho, Commented Nov 13, 2019 at 4:47

Seb · Accepted Answer · 2019-11-13 05:16:29Z

1

Have you tried this?

>>> bytes('cat', 'ascii')
b'cat'

For null termination simply add NUL:

>>> bytes('cat', 'ascii') + b'\x00'
b'cat\x00'

Edit: To store the hex representation in a string you could do something like this:

>>> ''.join(['\\'+hex(b)[1:] for b in bytes('cat', 'ascii')])
'\\x63\\x61\\x74'
>>> print(_)
\x63\x61\x74

edited Nov 13, 2019 at 5:16

answered Nov 13, 2019 at 4:35

Seb

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4 Comments

Flengo Over a year ago

I need the format of the result string to be in hex, as in "\x63\x61\x74"

Seb Over a year ago

It is already. b'cat' indicates a bytes object or bytestring and is identical to b'\x63\x61\x74'. If it's formatting you're after, you can get the hex representation like this: bytes('cat', 'ascii').hex().

juanpa.arrivillaga Over a year ago

@Flengo what, exactly do you want? Do you want a byte string that has the bytes you are representing in hex, or do you want that actual hex representation as a byte string?

Flengo Over a year ago

Sorry, I should have been more clear with my question. I need the hex representation as a string. So ultimately, I don't need b'cat' but I need '\x63\x61\x74' as a string instead, based on 'cat' or whatever else it might be.

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