I have code that expects str but will handle the case of being passed bytes in the following way:
if isinstance(data, bytes):
data = data.decode()
Unfortunately, this does not work in the case of bytearray. Is there a more generic way to test whether an object is either bytes or bytearray, or should I just check for both? Is hasattr('decode') as bad as I feel it would be?
ベストアンサー1
There are a few approaches you could use here.
Duck typing
Since Python is duck typed, you could simply do as follows (which seems to be the way usually suggested):
try:
data = data.decode()
except (UnicodeDecodeError, AttributeError):
pass
You could use hasattr as you describe, however, and it'd probably be fine. This is, of course, assuming the .decode() method for the given object returns a string, and has no nasty side effects.
I personally recommend either the exception or hasattr method, but whatever you use is up to you.
Use str()
This approach is uncommon, but is possible:
data = str(data, "utf-8")
Other encodings are permissible, just like with the buffer protocol's .decode(). You can also pass a third parameter to specify error handling.
Single-dispatch generic functions (Python 3.4+)
Python 3.4 and above include a nifty feature called single-dispatch generic functions, via functools.singledispatch. This is a bit more verbose, but it's also more explicit:
def func(data):
# This is the generic implementation
data = data.decode()
...
@func.register(str)
def _(data):
# data will already be a string
...
You could also make special handlers for bytearray and bytes objects if you so chose.
Beware: single-dispatch functions only work on the first argument! This is an intentional feature, see PEP 433.