Please help! I am new to Python.
I created a model in ModelBuilder. The last steps are to grab the attribute table of the feature class, sort MEAS column in ascending order and then subtract next value from current and load those values in the new field. (I have an empty field in the attribute table).
I wrote a simple script, but all I could do is to sort the MEAS column and print values out.
Could anybody be so kind and get me an example code?....
---Natalie- I've done something similar in the 9.3 scripting environment using some of Richard Crissup's code (he had an ArcScript posting on June 27, 2008 called date_diff.py). Basically, you start with a GPS generated track point shapefile with a time stamp field. To that, the python script adds a numeric double field, and in the new field, calculates the difference in hours between the timestamp field in each record and the next, so one can sum up the amount of time spent in an area. You have to know how the date field comes to you. The script takes a while to execute, but gets the job done.I'm new to Python, too, so please people, go easy on me, too:import arcgisscripting, sys, os, re
import time, calendar, string, decimal
def func_check_format(time_string):
if time_string.find("/") == -1:
print "Error: time string doesn't contain any '/' expected format \
is month/day/year hour:minutes:seconds"
elif time_string.find(":") == -1:
print "Error: time string doesn't contain any ':' expected format \
is month/day/year hour:minutes:seconds"
list = time_string.split()
if (len(list)) <> 2:
print "Error time string doesn't contain and date and time separated \
by a space. Expected format is 'month/day/year hour:minutes:seconds'"
def func_parse_time(time_string):
'''
take the time value and make it into a tuple with 9 values
example = "2004/03/01 23:50:00". If the date values don't look like this
then the script will fail.
'''
year=0;month=0;day=0;hour=0;minute=0;sec=0;
time_string = str(time_string)
l=time_string.split()
if not len(l) == 2:
gp.AddError("Error: func_parse_time, expected 2 items in list l got" + str(len(l)) + "time field value = " + time_string)
raise Exception
cal=l[0];cal=cal.split("/")
if not len(cal) == 3:
gp.AddError("Error: func_parse_time, expected 3 items in list cal got " + str(len(cal)) + "time field value = " + time_string)
raise Exception
ti=l[1];ti=ti.split(":")
if not len(ti) == 3:
gp.AddError("Error: func_parse_time, expected 3 items in list ti got " + str(len(ti)) + "time field value = " + time_string)
raise Exception
if int(len(cal[0]))== 4:
year=int(cal[0])
month=int(cal[1])
day=int(cal[2])
else:
year=int(cal[2])
month=int(cal[0])
day=int(cal[1])
hour=int(ti[0])
minute=int(ti[1])
sec=int(ti[2])
#formated tuple to match input for time functions
result=(year,month,day,hour,minute,sec,0,0,0)
return result
#----------------------------------------------------------------------------
def func_time_diff(start_t,end_t):
'''
Take the two numbers that represent seconds
since Jan 1 1970 and return the difference of
those two numbers in hours. There are 3600 seconds
in an hour. 60 secs * 60 min '''
start_secs = calendar.timegm(start_t)
end_secs = calendar.timegm(end_t)
x=abs(end_secs - start_secs)
#diff = number hours difference
#as ((x/60)/60)
diff = float(x)/float(3600)
return diff
#----------------------------------------------------------------------------
print "Executing getnextLTIME.py script..."
try:
gp = arcgisscripting.create(9.3)
# set parameter to what user drags in
fcdrag = gp.GetParameterAsText(0)
psplit = os.path.split(fcdrag)
folder = str(psplit[0]) #containing folder
fc = str(psplit[1]) #feature class
fullpath = str(fcdrag)
gp.Workspace = folder
fldA = gp.GetParameterAsText(1) # Timestamp field
fldDiff = gp.GetParameterAsText(2) # Hours field
# set the toolbox for adding the field to data managment
gp.Toolbox = "management"
# add the user named hours field to the feature class
gp.addfield (fc,fldDiff,"double")
#gp.addindex(fc,fldA,"indA","NON_UNIQUE", "ASCENDING")
desc = gp.describe(fullpath)
updateCursor = gp.UpdateCursor(fullpath, "", desc.SpatialReference, fldA+"; "+fldDiff, fldA)
row = updateCursor.Next()
count = 0
oldtime = str(row.GetValue(fldA))
#check datetime to see if parseable
func_check_format(oldtime)
gp.addmessage("Calculating " + fldDiff + " field...")
while row <> None:
if count == 0:
row.SetValue(fldDiff, 0)
else:
start_t = func_parse_time(oldtime)
b = str(row.GetValue(fldA))
end_t = func_parse_time(b)
diff_hrs = func_time_diff(start_t, end_t)
row.SetValue(fldDiff, diff_hrs)
oldtime = b
count += 1
updateCursor.UpdateRow(row)
row = updateCursor.Next()
gp.addmessage("Updated " +str(count+1)+ " rows.")
#gp.removeindex(fc,"indA")
del updateCursor
del row
except Exception, ErrDesc:
import traceback;traceback.print_exc()
print "Script complete."
