average time calculation??

[Oscar Benjamin]

On 10 January 2013 17:50, pmec <pcurad01 at gmail.com> wrote:
> Hi there guys i've got a script that's suppose to find the average of two times as strings. The times are in minutes:seconds:milliseconds
> i'm doing ok in printing the right minutes and seconds my problem is with the milliseconds.

You might find it easier to do this arithmetic if using datetime.time
objects from the datetime module:
http://docs.python.org/2/library/datetime.html

>
> Example if i have 00:02:20 and 00:04:40 the average will be 00:03:30 or 00:02:00 and 00:03:00 will be 00:02:30
>
> Can anyone help me out with this please. Here is the code that i have so far:
>
> def lap_average(lap1, lap2):
>
>     t1 = lap1.replace(":",'')
>     t2 = lap2.replace(":",'')
>
>     mins1, secs1, hundreths1 = t1[:2], t1[2:4], t1[4:]
>     mins2, secs2, hundreths2 = t2[:2], t2[2:4], t2[4:]

Are these really hundredths? At the top you said it goes
minutes:seconds:milliseconds. A hundredth of a second is 10
milliseconds so you need to be clear about which one you want.

>
>     total_seconds = int(secs1) + int(secs2) + int(mins1) * 60 + int(mins2) * 60

What happened to the hundredths in the line above. Surely you wanted
to add 0.01 * hundredths there.

>
>     millisec = (total_seconds * 1000)
>     millisec = millisec / 2

In Python 2 this division will always round down if millisec is an
integer. Is that what you want?

>
>     micro_x = millisec

Is the line above just there to confuse me? I thought millisec was a
good descriptive name. In this context micro would suggest
microseconds which would be 1000 times smaller.

>     minutes = micro_x / (60*1000)

Wouldn't it have been easier to just get this from total_seconds?

>     micro_x = micro_x - minutes * (60*1000)
>     seconds = micro_x / 1000

This will behave differently in Python 3. Safest to use floor division // here:
http://stackoverflow.com/questions/183853/in-python-what-is-the-difference-between-and-when-used-for-division

>     micro_x = micro_x - seconds

Surely that should be seconds*1000?

>
>    print '%02d:%02d:%s' % (minutes, seconds, micro_x)

Until your done debugging, I suggest you print all of these values out
directly (without the format string):

print(minutes, seconds, microx)

>
> lap_average('03:40:00', '05:20:00')
> lap_average('03:00:02', '02:00:00')
> lap_average('02:25:50', '06:50:75')
> lap_average('00:02:00', '00:03:00')
> lap_average('00:02:20', '00:04:40')
> lap_average('02:40:40', '03:30:30')
> lap_average('02:60:30', '60:40:40')


Oscar