python time problem

Question

Hello,

I am using the exif.py library. After calling

tags=exif.process_file(...)

i want to retrieve the time the image was captured. so i continue with

t =tags['Image DateTime'] if tags.has_key('Image DateTime') else time.time()

now i want to store t in django's database. For that t must be in the form 2010-07-20 14:37:12 but apparently exif delivers 2010:07:20 14:37:12 however when i go

type(t)

it returns 'instance' as opposed to float which is the result of

type(time.time())

or 'str' which is the type of string. How can I parse the value EXIF gave me to stuff it into the django model?

Answer 1

It looks like exif.py returns an instance of IFD_Tag. The values you want may be in t.values. You can also use datetime.strptime() to parse the string you get from the exif data.

Answer 2

Django works best with datetime objects. Strings can be converted to datetime, but you should not focus on strings. You should focus on creating a proper datetime object.

Choice 1. Figure out what actual class the exif time is. Instead of type(t), do t.__class__ to see what it really is. Also, so dir(t) to see what methods it has. It may have methods which will create a proper float value or time.struct_time value.

Choice 2. Parse the time string with datetime.datetime.strptime to create a proper datetime object. Read this: http://docs.python.org/library/datetime.html#datetime.datetime.strptime

Answer 3

Use time.strptime() to parse the str() value, than format the time tuple to any desired form.

An example, using the 'Image DateTime' attribute returned by EXIF.

>>> e1['Image DateTime']
(0x0132) ASCII=2007:09:06 06:37:51 @ 176
>>> str(e1['Image DateTime'])
'2007:09:06 06:37:51'
>>> 
>>> tag = time.strptime(str(e1['Image DateTime']),"%Y:%m:%d %H:%M:%S")
>>> tag
time.struct_time(tm_year=2007, tm_mon=9, tm_mday=6, tm_hour=6, tm_min=37, tm_sec=51,tm_wday=3, tm_yday=249, tm_isdst=-1)
>>> time.strftime("%Y-%m-%d %H:%M:%S", tag)
'2007-09-06 06:37:51'
>>> 

Answer 4

Assuming that tags['Image DateTime'], if present, returns a string like "2010:07:20 14:37:12" then you can use:

if tags.has_key('Image DateTime'):
    t = tags['Image DateTime'].replace(':', '-' , 2)
else:
    t = time.strftime('%Y-%m-%d %H:%M:%S')

replace fixes the time-string from exif:

>>> '2010:07:20 14:37:12'.replace(':', '-', 2)
    '2010-07-20 14:37:12'

If you want GMT rather than local time use

time.strftime('%Y-%m-%d %H:%M:%S', time.gmtime())