4

I am a beginner with Python and having trouble calculating time intervals.

I'll explain the data structure first. The second element in each list in sg_status is a code standing for certain status of traffic signal light. The code '0','1','3' represent minimum green status of traffic light. I want to calculate the time duration of minimum green. The definition of one minimum_green duration is that the start time of first other status next to a minimum_green_status subtracts the start time of the minimum_green_status. Then, add the minimum green time in a list.

My solution:

def get_minimum_green(sg_status):   
    minimum_green_list = [] 
    start_time_green = None 
    for i in range(len(sg_status)):
        if not(sg_status[i][1] == '3' or sg_status[i][1] == '1' or sg_status[i][1] == '0' and \
        (i != 0 and sg_status[i-1][1] != '3' and sg_status[i-1][1] != '1' and sg_status[i-1][1] != '0')) :
            continue
        else:
            start_time_green = sg_status[i][0]

            for j in range(i,len(sg_status)):
                if not(sg_status[j][1] != '3' and sg_status[j][1] != '1' and sg_status[j][1] != '0' and \
                (sg_status[j-1][1] == '3' or sg_status[j-1][1] == '1' or sg_status[j-1][1] == '0')):
                    continue
                else:
                    end_time_green = sg_status[j][0]
                    print "start: "+str(start_time_green)
                    print "end  :" + str(end_time_green)
                    minumum_green = end_time_green - start_time_green
                    minimum_green_list.append(minumum_green) 
                    break 

    return str(minimum_green_list)

But the result is obviously wrong and it prints more start_time_green than the correct ones. I doubt the filter 

   if not(sg_status[i][1] == '3' or sg_status[i][1] == '1' or sg_status[i][1] == '0' and \
                (i != 0 and sg_status[i-1][1] != '3' and sg_status[i-1][1] != '1' and sg_status[i-1][1] != '0'))

or logic about this is incorrect.

sg_status =[[[datetime.datetime(2015, 7, 8, 3, 0, 24, 302000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'], 
             [datetime.datetime(2015, 7, 8, 3, 0, 24, 903000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 0, 27, 600000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 0, 28, 201000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 0, 37, 500000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 0, 38, 101000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 40, 500000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 41, 1000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 50, 600000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 50, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 51, 502000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 55, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 55, 901000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 57, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 1, 58, 703000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '<'],
             [datetime.datetime(2015, 7, 8, 3, 2, 1, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'A'],
             [datetime.datetime(2015, 7, 8, 3, 2, 2, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'A'],
             [datetime.datetime(2015, 7, 8, 3, 2, 3, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 7, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 10, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 11, 802000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 12, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 12, 801000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 13, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 14, 703000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 15, 704000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 16, 705000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 16, 806000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 18, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 20, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 21, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 22, 903000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 23, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 24, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 25, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 26, 703000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 2, 26, 804000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '0'],
             [datetime.datetime(2015, 7, 8, 3, 2, 27, 805000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '1'],
             [datetime.datetime(2015, 7, 8, 3, 2, 30, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '1'],
             [datetime.datetime(2015, 7, 8, 3, 2, 32, 801000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 2, 35, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 3, 51, 400000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 3, 52, 1000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 3, 58, 500000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 3, 59, 101000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 17, 900000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 18, 401000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 24, 800000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 25, 301000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 25, 902000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 26, 603000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 28, 704000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 29, 305000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 35, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 5, 35, 601000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 12, 100000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 13, 1000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 15, 402000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 15, 903000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 17, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 19, 1000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 19, 402000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 23, 800000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 24, 501000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 25, 802000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 26, 303000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 26, 704000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 27, 205000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 27, 906000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 28, 500000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 30, 801000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 31, 302000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 33, 200000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 33, 901000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 37, 402000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 38, 100000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 49, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 54, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 56, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '3'],
             [datetime.datetime(2015, 7, 8, 3, 8, 57, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), '<'],
             [datetime.datetime(2015, 7, 8, 3, 9, 0, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'A'],
             [datetime.datetime(2015, 7, 8, 3, 9, 1, 701000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'A'],
             [datetime.datetime(2015, 7, 8, 3, 9, 2, 702000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 9, 6, 700000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 9, 7, 301000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 9, 8, 402000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 9, 9, 203000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],
             [datetime.datetime(2015, 7, 8, 3, 9, 9, 704000, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=180, name=None)), 'B'],]
chenchenmomo
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  • Did you know that, in python you can use \ to break a single line over multiple ones. You might want to consider using it. See [this](http://stackoverflow.com/questions/53162/how-can-i-do-a-line-break-line-continuation-in-python) – Rohcana Aug 04 '15 at 14:04

1 Answers1

2

This can be accomplished using a single loop.

  1. Initialize an empty green_time_list to store times for green intervals, green_on=False to signify green is not currently on and green_start time to None
  2. If green is on and current status is not one of '0', '1', '3', then this is the first non-green entry. Set green to off and compute time difference between green_start and timestamp of current entry. Add the time-difference to green_time_list
  3. Otherwise if green is off and current status is one of '0', '1', '3', then this is first "green" entry. Set green to on and save timestamp in green_start_time

This of course assumes your data is in chronological order

def find_green_times(sg_status):
    green_on = False
    green_list = []
    green_start = None
    for s in sg_status:
        if not green_on and s[1] in ("0","1","3"):
            # Green was not on till now and now  a green status is seen
            # Save timestamp as green_start time
            green_start = s[0]
            # Set green is on
            green_on = True
        elif green_on and s[1] not in ("0", "1", "3"):
            # Green was on and a non-green status is seen
            # Set green to off 
            green_on = False
            # Compute time difference between time when green was
            # started and this timestamp
            green_list.append(s[0] - green_start)
            # Optionally reset the green time
            green_start = None
    return green_list, green_on, green_start

Then for your given input this returns

>>> find_green_times(sg_status)
([datetime.timedelta(0, 94, 401000), datetime.timedelta(0, 390, 898000)], False, None)
RedBaron
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