Using ArcGIS Desktop field calculator (python) to parse date

Question

I'm trying to parse a datetime field using python (but have never used python for it before). I have a field that contains a valid date, but not a valid time... and other fields that have valid hour and am/pm information. I need to grab the date (mm/dd/yy) from the datetime field and then combine that with the valid hour and am/pm fields into a new string field.

Below is the vbscript way that I would do this (and it works fine, but I need to build it using python):

    (DatePart ( "m", [STARTDATE])) &"/"& 
    (DatePart ("d", [STARTDATE] )) &"/"& 
    (DatePart ("yyyy", [STARTDATE] )) &" until "&  
    (DatePart ( "m", [ENDDATE])) &"/"& 
    (DatePart ("d", [ENDDATE] )) &"/"& 
    (DatePart ("yyyy", [ENDDATE] )) &" (from "&
    [StartHour] &" "&
    [StartAMPM] &" until "& 
    [EndHour] &" "& 
    [EndAMPM]&" )"

Here's what I've written so far using python (but doesn't work):

    def dateFull(oid)
    startDateObj = datetime.datetime.strptime( !STARTDATE! , "%m/%d/%Y")
    endDateObj = datetime.datetime.strptime( !ENDDATE! , "%m/%d/%Y")
    return startDateObj + " to " +  endDateObj + " from " + !StartHour! + " " + !StartAMPM! + " to " + !EndHour! + " " + !EndAMPM!

Can someone please help me figure out what I'm doing wrong here?

Answer 1

Set the python parser (don't use codeblock). I assume all input fields (!StartHour!,...) are string or date. if not bracket it with str() function

standalone python code:

startdate =  '3/1/15'
enddate =  '2/15/15'

starthour = "5"
startAMPM = "PM"
endhour = "6"
endAMPM = "AM"

print str.format("{0} to {1} from {2} {3} to {4} {5}",
startdate,
enddate,
starthour,
startAMPM,
endhour,
endAMPM)

Field calculator:

str.format("{0} to {1} from {2} {3} to {4} {5}",
!startdate!,
!enddate!,
!starthour!,
!startAMPM!,
!endhour!,
!endAMPM!)

Answer 2

It sounds like your issue is more with the malformed dates (some have times, some don't, etc...) than anything else.

You should be able to use a simple Python expression in the field calculator like this:

'{0} to {1} from {2} {3} to {4} {5}'.format(!STARTDATE!.split(' ')[0],
                                            !ENDDATE!.split(' ')[0],
                                            !StartHour!, !StartAMPM!,
                                            !EndHour!, !EndAMPM!)

The important part is the .split(' ')[0] bit. That will return just the date part for dates that have a time and won't fail for those that don't.

Another thing to note is that CalculateField passes dates to Python as strings instead of datetime objects for some reason (so no need to cast).