Writing an ASCII string as binary in python

Question

I have a ASCII string = \"abcdefghijk\". I want to write this to a binary file in binary format using python.

I tried following:

str  = \"abcdefghijk         


        

Answer 1

You misunderstood what \xhh does in Python strings. Using \x notation in Python strings is just syntax to produce certain codepoints.

You can use '\x61' to produce a string, or you can use 'a'; both are just two ways of saying give me a string with a character with hexadecimal value 61, e.g. the a ASCII character:

>>> '\x61'
'a'
>>> 'a'
'a'
>>> 'a' == '\x61'
True

The \xhh syntax then, is not the value; there is no \ and no x and no 6 and 1 character in the final result.

You should just write your string:

somestring = 'abcd'

with open("test.bin", "wb") as file:
    file.write(somestring)

There is nothing magical about binary files; the only difference with a file opened in text mode is that a binary file will not automatically translate \n newlines to the line separator standard for your platform; e.g. on Windows writing \n produces \r\n instead.

You certainly do not have to produce hexadecimal escapes to write binary data.

On Python 3 strings are Unicode data and cannot just be written to a file without encoding, but on Python the str type is already encoded bytes. So on Python 3 you'd use:

somestring = 'abcd'

with open("test.bin", "wb") as file:
    file.write(somestring.encode('ascii'))

or you'd use a byte string literal; b'abcd'.

Answer 2

I think you don't necessarily understand what binary/ascii is ... all files are binary in the sense that its just bits. ascii is just a representation of some bits... 99.9999 % of file editors will display your bits as ascii if they can , and if there is no other encoding declared in the file itself ...

fp.write("abcd") 

is exactly equivelent to

fp.write("\x61\x62\x63\x64")