Get a string from bytes until null

Question

Given a bytes object and an index, I want to read a string from the bytes between the index and the next null(\x00). For example:

bstr=b'abc\x00defg'
addr_to_str(bstr,0) # 'abc'
addr_to_str(bstr,1) # 'bc'
addr_to_str(bstr,4) # 'defg'

I can do the following:

def addr_to_str(bstr,i):
    return bstr[i:].split(b'\x00')[0].decode('utf-8')

Since the bytes object is very large, I would like an efficient version of addr_to_str. I am new to Python and not knowing how the interpreter treats the split() call when I only want to access the first split result. Or is the .decode() necessary?

Question: Is there a better and pythonic way to do addr_to_str()?

bytes.split() has an optional maxsplit argument...or you could use bytes.partition() which only does one. — martineau
– martineau, Commented Feb 23, 2015 at 21:18

NPE · Accepted Answer · 2015-02-23 21:29:25Z

1

How about (in Python 2):

def addr_to_str(s, pos):
   end = s.find('\0', pos + 1)
   if end != -1:
      return s[pos:end]
   else:
      return s[pos:]

This scans the string once looking for a null, and then creates a slice.

edited Feb 23, 2015 at 21:29

answered Feb 23, 2015 at 21:14

NPE

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4 Comments

Peng Zhang Over a year ago

s is a bytes not a string. It complains s.find('\0',). The function should take a bytes and return a string.

NPE Over a year ago

Works for me in Python 2.7. If you're using Python 3, you might want to specify that.

Peng Zhang Over a year ago

So, in Python 3, seem that the .decode() needs to be explicitly called.

roeland Over a year ago

In python 3, for bytes, use s.find(b'\0', pos + 1)

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