Write and read Datetime to binary format in Python

Question

I want to store a list of datetimes in a binary file in Python.

EDIT: by \"binary\" I mean the best digital representation for each datatype. The application for thi

Answer 1

If you want to save an object to a binary file, you may think about pickle

As far as I know, it writes a byte stream, so it's binary enough, but the result is

Python-specific

Also, I think it should work with datetime.

And you'll have this for saving:

with open('your_file', 'wb') as file:
    pickle.Pickler(file).dump(your_var)

And this for recovering

with open('your_file', 'rb') as file:
     recovered=pickle.Unpickler(file).load()

Answer 2

I have found a way using the Unix timestamp and storing it as an integer. This works for me because I don't need a subsecond resolution, but I think long integers would allow for microsecond resolution with some modifications of the code.

The changes from my original consist in replacing calendar.timegm by time.mktime and also utctimetuple by timetuple, to keep everything naive.

This:

import datetime
import struct
import time

now = datetime.datetime.now()
print now

stamp = time.mktime(now.timetuple())
print stamp

recoverstamp = datetime.datetime.fromtimestamp(stamp)
print recoverstamp

binarydatetime = struct.pack('<L', stamp)
recoverbinstamp = struct.unpack('<L', binarydatetime)[0]
print recoverbinstamp

recovernow = datetime.datetime.fromtimestamp(recoverbinstamp)
print recovernow

Returns this:

2013-09-02 11:06:28.064000
1378130788.0
2013-09-02 11:06:28
1378130788
2013-09-02 11:06:28

From this, I can easily write the packed binarydatetime to file, and read it back later.

Answer 3

By far the most simple solution is to use Temporenc: http://temporenc.readthedocs.org/

It takes care of all the encoding/decoding and allows you to write a Python datetime object to a file:

now = datetime.datetime.now()
temporenc.pack(fp, now)

To read it back, this suffices:

dt = temporenc.unpack(fp)
print(dt)