Everybody hates this one :) (bytes indexing)

This commit is contained in:
Antoine Pitrou 2011-02-05 12:13:38 +00:00
parent e6a1464b89
commit bd866e972c
1 changed files with 31 additions and 0 deletions

View File

@ -367,6 +367,37 @@ To turn the warning into an exception, use the ``-bb`` flag instead::
BytesWarning: Comparison between bytes and string
Indexing bytes objects
''''''''''''''''''''''
Another potentially surprising change is the indexing behaviour of bytes
objects in Python 3::
>>> b"xyz"[0]
120
Indeed, Python 3 bytes objects (as well as :class:`bytearray` objects)
are sequences of integers. But code converted from Python 2 will often
assume that indexing a bytestring produces another bytestring, not an
integer. To reconcile both behaviours, use slicing::
>>> b"xyz"[0:1]
b'x'
>>> n = 1
>>> b"xyz"[n:n+1]
b'y'
The only remaining gotcha is that an out-of-bounds slice returns an empty
bytes object instead of raising ``IndexError``:
>>> b"xyz"[3]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IndexError: index out of range
>>> b"xyz"[3:4]
b''
``__str__()``/``__unicode__()``
'''''''''''''''''''''''''''''''
In Python 2, objects can specify both a string and unicode representation of