Parse Binary Data File and convert Epoch Time

[drdevereaux]

Hello All!

I am trying to extract and convert data from a binary data file. Each data entry follows this order:

• sample time in seconds since unix epoch, 4 bytes
  
• 2 byte integer
  
• 2 byte integer
  
• 2 byte integer
  
• 2 byte integer
  

All values are integers

Below is the code I'm using based off a different binary data extraction project. It exports the correct number of data entries but the values do not make sense. I know I'm not parsing the binary file correctly but I;m not sure how to do the date conversion. Thanks!

import math, struct, time field_names = ('time1', 'vol_conc', 'part_size', \ 'opt_trans', 'laser_ref') def decode(data, offset=0): '''Decipher a lisst datagram from binary''' # Offset now tells it how far to start with open('li0002a', 'rb') as data: values = struct.unpack('i4h', data.read(12)) # Create a dictionary for all the values lisst_values = dict(zip (field_names, values)) return lisst_values def lisst_print(lisst_values): 'Print out all the values of a lisst dictionary' print 'results:' for key in lisst_values: print ' ', key, lisst_values[key] datagram_size = 12 # 2*6 bytes per datagram def num_datagrams(data): #How many packets are in data' # Make sure we have an even number of datagrams #assert (len(data) % datagram_size == 0) return len(data) / datagram_size def get_offset(datagram_number): 'Calculate the starting offset of a datagram' return datagram_number * datagram_size def main(): lisst_file = open('li0002a') lisst_data = lisst_file.read() print 'Number of datagrams:', num_datagrams(lisst_data) print 'Datagram Number, Time, Volume Concentration, Particle Size,\ Optical Transmission, Laser Reference ' for datagram_index in range( num_datagrams(lisst_data) ): offset = get_offset(datagram_index) datagram = decode(lisst_data,offset) print datagram_index, datagram['time1'], datagram['vol_conc'], datagram['part_size'], \ datagram['opt_trans'], datagram['laser_ref'] if __name__=='__main__': main()

[Larz60+]

pure binary as in a block of memory is arranged in machine addressing order, big or little endian, so your 4 byte value.
so you may have to do some transformations, Here's a good doc for that: https://wiki.python.org/moin/BitManipulation