Most concise, Pythonic way to represent a null byte as a binary (bytes) string in Python 3

Question

I needed to add some padding to a bytes string. This is what I came up with:

if padding_len > 0:
    data += bytes.fromhex('00') * padding_len

Is there a nicer way of representing a null byte in Python 3 than bytes.fromhex('00')?

Use bytes literal: b'\0'. bytes(padding_len) will give you padding_len bytes (filled with 0) — falsetru
– falsetru, Commented Aug 9, 2015 at 14:15

Patrick Maupin · Accepted Answer · 2015-08-09 14:49:41Z

3

>>> bytes.fromhex('00') == b'\x00'
True
>>> b'\x00' * 10
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'

EDIT:

As hobbs points out in a comment below, it is certainly possible to use b'\0' instead of b'\x00' and as j-f-sebastian points out, it is not confusing in this instance.

But I wouldn't do it, anyway. It certainly works in this context (and it saves you two characters, if that's important). It will even work in the most common other context, where you are building strings for C and putting a null byte at the end.

But in the most general case, it can lead to confusion, because the compiler's interpretation of b'\0' is highly data dependent. In other words, it changes according to what comes after that zero.

>>> b'\0ABC' == b'\00ABC'
True
>>> b'\0ABC' == b'\000ABC'
True
>>> b'\0ABC' == '\0000ABC'
False

If you are debugging late at night when not all your brain cells are functioning, it is highly frustrating to have the length of a string change because you replaced a character in the string. All you have to do to avoid this is to always use two extra characters. It doesn't matter whether you use \x00 (hexadecimal) or \000 octal -- both of those will work properly no matter the value of the following character.

edited Aug 9, 2015 at 14:49

answered Aug 9, 2015 at 14:14

Patrick Maupin

8,1672 gold badges25 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

hobbs Over a year ago

Or b"\0" for that matter.

Patrick Maupin Over a year ago

That works, but personally I wouldn't go there, unless the goal is to generate more questions. It's confusing that b'\0x' == b'\x00x' but b'\01' == b'\x01'

jfs Over a year ago

b'\0' is not confusing for a Python programmer.

Collectives™ on Stack Overflow

Most concise, Pythonic way to represent a null byte as a binary (bytes) string in Python 3

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related