Noobie: Open file -> read characters & multiply

[Scott David Daniels]

gonzlobo wrote:
> I've been using Python for a few days. It's such the perfect language
> for parsing data!
> 
> I really like it so far, but I'm having a hard time reading a file,
> reading the first few hex characters & converting them to an integer.
> Once the characters are converted to an integer, I'd like to write the
> data to another file.
> 
> Here's the code snipped to the bare minimum:
> ---
> # Open File
> AP_File= open("AP.txt", "r")
> decoded_File= open("decoded.txt", "w")
> 
> # read & process data line by line
> for line in AP_File:
>   time = int(hex(line[0:8]), 16) * 0.0001     # this line is completely 
> hosed!
>   decodedFile.write(time)
> 
> #close files
> AP_File.close()
> decoded_File.close()
> ---
> AP.txt
> 000000d5 26 0600 80 00 ec 80 02 03 7d db 02 33
> 000000d5 26 0601 80 00 80 00 02 37 fe 54 01 09
> 000000d5 06 0602 80 00 e0 00 01 29 fe d2 69 99
> 000000d5 06 0603 80 00 e0 00 02 29 fe d2 6a 99
> 000000d5 26 0604 80 00 fe 54 02 09 80 00 01 5d
> 000000d5 06 0605 80 00 e0 00 02 15 fc 71 ca 0b
> 000000d5 4a 0610 81 00 86 00 02 26 12 00 02 a6
> 000000d5 4f 0611 00 00 00 50 00 00 00 00 07 00
> 000000d5 06 0612 80 00 e0 00 01 15 fc 71 c9 0b
> 000000d5 0a 0613 08 5c 04 88 08 98 00 00 00 00
> 000000d5 06 0614 80 00 e0 00 02 01 60 79 82 2b
> 000000d5 0a 0615 08 00 00 00 00 00 00 00 00 00
> 000000d5 26 0616 80 00 80 00 02 5d 04 22 3a 88
> (actual files are 250MB!)
> 
> decodedTime.txt (should be)
> 0.0213 26 0600 80 00 ec 80 02 03 7d db 02 33
> ...
> 
> My boss and I are trying to complete the same task (he figured out how
> to do it, but his code uses a while != "" loop and doesn't look
> pythony (it looks too 'c'). Not that there's anything wrong with that!
> 
> Any help is really appreciated.
for line in AP_file:
     print >>decoded_File, '%s.%04d' % divmod(int(line[:8], 16), 10000
                                              ), line[9:].rstrip()

or:

for line in AP_file:
     print >>decoded_File, '%.4f' % (int(line[:8], 16) * .0001
                                              ), line[9:].rstrip()


--Scott David Daniels
scott.daniels at acm.org