[Tutor] dbus.Array to string

[Amit Saha]

On Mon, Aug 12, 2013 at 11:04 AM, Steven D'Aprano <steve at pearwood.info> wrote:
> On 12/08/13 08:53, Amit Saha wrote:
>>
>> Hello all,
>>
>> The other day, I had to convert a dbus.Array [1] object to a string. I
>> found a way to do it, but I am not sure if that is the best way.
>
>
>
> Does the Array object not have a "toString" method? Or similar?

No, not from what I see.
>
> What do you get when you call str() or repr() on the Array object?

>> str(ssid)
"dbus.Array([dbus.Byte(66), dbus.Byte(105), dbus.Byte(103),
dbus.Byte(80), dbus.Byte(111), dbus.Byte(110), dbus.Byte(100),
dbus.Byte(54), dbus.Byte(55), dbus.Byte(57), dbus.Byte(68),
dbus.Byte(56), dbus.Byte(53)], signature=dbus.Signature('y'),
variant_level=1)"


>
>
>
>> Here is a dbus.Array object:
>>
>> dbus.Array([dbus.Byte(66), dbus.Byte(105), dbus.Byte(103),
>> dbus.Byte(80), dbus.Byte(111), dbus.Byte(110), dbus.Byte(100),
>> dbus.Byte(54), dbus.Byte(55), dbus.Byte(57), dbus.Byte(68),
>> dbus.Byte(56), dbus.Byte(53)], signature=dbus.Signature('y'),
>> variant_level=1)
>
>
>
> Basically it is an array of bytes, with a couple of extra arguments. Do you
> care about the signature and variant_level arguments?

No, I don't care about the the signature and variant_level arguments.


>
>
>
>
>> And this is how I converted it to it's string representation:
>
>
> Careful. In usual Python terminology, the string representation of an
> object, or just repr, is the string that represents how the object is
> created, more or less. So the string representation would be something like:
>
> "Array([Byte(66), Byte(105), ..., Byte(53)], signature=Signature('y'),
> variant_level=1)"
>
> which is nothing like what you want.
>
>
>
>>>>> import dbus
>>
>>
>>>>> ssid = "dbus.Array([dbus.Byte(66), dbus.Byte(105), dbus.Byte(103),
>>>>> dbus.Byte(80), dbus.Byte(111), dbus.Byte(110), dbus.Byte(100),
>>>>> dbus.Byte(54), dbus.Byte(55), dbus.Byte(57), dbus.Byte(68), dbus.Byte(56),
>>>>> dbus.Byte(53)], signature=dbus.Signature('y'), variant_level=1)
>>
>> "
>
>
> Here you create a string, which looks like "dbus.Array(...)".
>
>
>
>>>>> ssid = ''.join([chr(character) for character in ssid])
>
>
> Since ssid is already a string, iterating over it gives you characters;
> calling chr() on a character raises an exception.

Sorry, ssid wasn't supposed to be a string, of course.
>
>
>>>>> ssid
>>
>> 'BigPond679D85'
>
>
> Not with the code you provide.
>
>
> If you drop the quotation marks around the dbus.Array, so you get an Array
> object instead of a string, then your code may work. But look at your list
> comprehension:
>
>
> [chr(character) for character in ssid]
>
> That's confusing. If iterating over ssid gives characters, as the code
> claims, then there is no need to call chr(), and in fact you wouldn't need
> the list comp at all, you could just say:
>
> ''.join(ssid)
>
>
> But it isn't an array of characters, it is an array of bytes. So:
>
> ''.join([chr(byte) for byte in ssid])
>
> is less misleading and confusing.

Agree.

>
> Another alternative:
>
> ''.join(map(chr, ssid))
>
>
> is more terse, but may not be as readable to those who aren't familiar with
> map. Both forms should be more or less equally as efficient.

Right.

Just for the sake of correctness:

>>> import dbus
>>> ssid=dbus.Array([dbus.Byte(66), dbus.Byte(105), dbus.Byte(103), dbus.Byte(80), dbus.Byte(111), dbus.Byte(110), dbus.Byte(100), dbus.Byte(54), dbus.Byte(55), dbus.Byte(57), dbus.Byte(68), dbus.Byte(56), dbus.Byte(53)], signature=dbus.Signature('y'), variant_level=1)

>>> temp_ssid = ''.join([chr(byte) for byte in ssid])
>>> temp_ssid
'BigPond679D85'



Thanks,
Amit.



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