[Python-Dev] A better and more basic array type (original) (raw)

Dennis Heuer dh at triple-media.com
Thu Apr 27 16:01:43 CEST 2006

Yes, this was previously "inheriting basic types more efficiently" but now I want something different ;)

I looked at the array type and found it quite C-ish. It is also not suited for arithmetics because it's a sequence type like a constrained list and not efficiently (and comfortably) usable like a sliceable integer. I'd rather like to find a basic built-in array type in python, which doesn't even ask for the format but just deals with the technical issues internally. This array type works like the long type but is mutable and supports slicing (focusing on a bit-range in the presentation of the number). The advantage of this array is that it is fully supporting arithmetics--even on slices--, that there is no need for boundary-checking, and that this mutable array type is actually usable as a superclass for new types. The other type of array, the constrained list, is inclusive:

x = array() x += 255 # x now holds the number 255 or, in other words, the first # 8 bits are set to 1 x += "1010" # x interprets "1010" as a bit-pattern and adds 10 x.step(8) # telling x that, from now on, a unit is 8-bit long # (for correct slicing and iteration; this is not # related to the real/internal array layout) x[:] = 0 # clearing all bits or setting x to zero f = open("binary file", "rb") x += f.read() for n in x: # n holds always the next 8 bit (a byte) y = x[4:6] # stores the fifth and the sixth byte in y x.step(1) # telling x that, from now on, a unit is 1-bit long z = x[4:6] # stores the fifth and the sixth bit in z x[0:2] = z # overwrites the first two bits in x with the two bits in z

Possibly the step attribute can become problematic and it's better to define a fix step at initialization. Smaller bit-packages from otherwise compatible types could be packed up with trailing zeroes.

I hope that somebody agrees and is already starting to implement this new array type. My best wishes are with you.

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