Inefficient way to process binary data, posted on codereview.SE: http://codereview.stackexchange.com/q/117080/61165

findCoincidences_5byte_numpy.py

#!/usr/bin/python3
import os
import numpy as np

# ============ CONSTANTS TO (OPTIONALLY) SET =============
WINDOW_SIZE = 100
INPUT_FILE_NAME = 'timetags5byte.bin'

# ======== CODE TO READ AND PARSE 5 BYTE BINARY FILE =========================
# process data in INPUT_FILE_NAME and print results in OUTPUT_FILE_NAME
with open(INPUT_FILE_NAME, 'rb') as input_file:

    # number of bytes found in every file produced when writing the binary file
    initial_offset = 40
    # number of bytes occupied by each timetag
    timetag_size = 5

    # each timetag is stored in 5 bytes. The first 4 bytes contain the
    # timestamp, with the first byte being the least significant one, and last
    # byte the most significant one
    file_size = os.path.getsize(INPUT_FILE_NAME)
    effective_file_size = file_size - initial_offset - file_size % 5
    input_file.seek(initial_offset)
    timetags = np.fromfile(input_file,
        dtype = np.dtype([('timestamp', np.uint32), ('channel', np.uint8)]),
        count = effective_file_size
        )

    # output_channels will contain the data to export (in file or whatever)
    output_channels = []
    # the first timetag is read out of the loop, in order to avoid checking
    # at each iteration if coincidences is empty.
    triggering_timestamp = timetags[0][0]
    channels = [timetags[0][1]]
    # Loop over all the timetags, except for the first one
    for timetag in timetags[1:]:
        if (timetag[0] > triggering_timestamp and 
            timetag[0] - triggering_timestamp < WINDOW_SIZE
            ):
            channels.append(timetag[1])
        else:
            if len(channels) == 4:
                print("fourfold coincidence:", end='')
                for channel in channels:
                    print('{0: >5}'.format(channel), end='')
                print('')
                output_channels.append(channels)
            channels = [timetag[1]]
            triggering_timestamp = timetag[0]
    if len(channels) == 4:
        print("fourfold coincidence:", end='')
        for channel in channels:
            print('{0: >5}'.format(channel), end='')
        print('')
        output_channels.append(channels)