faster bit transitions

bitarray_test.py

import bitarray
import time
import numpy as np
a = np.arange(100000, dtype=np.uint64)

def transitions(a):
    b = bitarray.bitarray()
    b.frombytes(a.tostring())
    c=b.itersearch(bitarray.bitarray("01"))
    return [d for d in c]

def find_01_bit_transitions(bitvector, nbits=64, prev_trig_state=False):
    '''Given a vector of bits, return an array of sample numbers in which a 0->1
    bit transition occurred.  It is assumed that only the lowest <nbits> bits in
    each data value need to be checked.

    Here, "sample number" means row number. We're assuming that <nbits> is equal
    to the number of rows in the data stream. The sample numbers will be with respect
    to the first frame in the bitvector.
    '''

    transitions = []
    fully_on = 0
    for _ in range(nbits):
        fully_on = (fully_on<<1) | 1

    on_state = prev_trig_state
    for i in xrange(len(bitvector)):
        bp = int(bitvector[i])
        if not on_state and (bp==0): continue
        if on_state and (bp==fully_on): continue

        for j in xrange(nbits):
            thisbit = bool(bp & 1)
            bp = bp>>1
            if on_state != thisbit:
                on_state = thisbit
                if on_state:
                    rownum = j+(i*nbits)
                    transitions.append(rownum)
    return transitions

t1 = time.time()
transitions(a)
t2 = time.time()
print(t2-t1) # 0.0973989963531

t1 = time.time()
find_01_bit_transitions(a)
t2 = time.time()
print(t2-t1) # 1.92169213295

sudo port install py27-bitarray to get the package
have I mentioned that I think package management in python is a clusterfuck after experiencing julia?