topic Re: Convert Date to yyyymmdd string in field calculator with Python in Python Questions

Convert Date to yyyymmdd string in field calculator with Python

NealBanerjee — Fri, 31 May 2019 12:16:53 GMT

Hello,

I am stuck with syntax for what I think will be very easy task. I have a feature class with a date field that I simply want to convert to a string field in yyyymmdd format, so that I can combine it with other fields to create a unique ID.

Id like to do this in a simple field calculator (in ArcMap) session with python

I tried using the strftime method with simple expression but that doesnt work !mydatefield!.strftime('%Y%m%d'). I also tried a few other things but keep getting error

Any help would be greatly appreciated!

Thanks

Neal

Re: Convert Date to yyyymmdd string in field calculator with Python

MitchHolley1 — Sun, 12 Dec 2021 02:20:40 GMT

This is kind of a long-winded answer, but it should give you the results you're looking for. Since you did not specify, I assume your date field is in a format like this 5/31/2019.

date = str'5/31/2019'
ds = date.split('/')
formatted = ds[2] + ds[0] + ds[1]

>>> formatted
'2019531'‍‍‍‍‍‍‍‍‍‍‍‍

Re: Convert Date to yyyymmdd string in field calculator with Python

TedKowal — Sun, 12 Dec 2021 02:20:42 GMT

If you are starting with an actual datetime field [dt]:

import datetime 
dt = datetime.datetime(2019, 5, 31, 0, 0)

dt.strftime('%Y%m%d')

'{:%Y%m%d}'.format(dt)

For completeness' sake: you can also directly access the attributes of the object, but then you only get the numbers:

'%Y%m%d' % (dt.month, dt.day, dt.year)

For reference, here are the codes used in format string:

%a Weekday as locale’s abbreviated name.
%A Weekday as locale’s full name.
%w Weekday as a decimal number, where 0 is Sunday and 6 is Saturday.
%d Day of the month as a zero-padded decimal number.
%b Month as locale’s abbreviated name.
%B Month as locale’s full name.
%m Month as a zero-padded decimal number. 01, ..., 12
%y Year without century as a zero-padded decimal number. 00, ..., 99
%Y Year with century as a decimal number. 1970, 1988, 2001, 2013
%H Hour (24-hour clock) as a zero-padded decimal number. 00, ..., 23
%I Hour (12-hour clock) as a zero-padded decimal number. 01, ..., 12
%p Locale’s equivalent of either AM or PM.
%M Minute as a zero-padded decimal number. 00, ..., 59
%S Second as a zero-padded decimal number. 00, ..., 59
%f Microsecond as a decimal number, zero-padded on the left. 000000, ..., 999999
%z UTC offset in the form +HHMM or -HHMM (empty if naive), +0000, -0400, +1030
%Z Time zone name (empty if naive), UTC, EST, CST
%j Day of the year as a zero-padded decimal number. 001, ..., 366
%U Week number of the year (Sunday is the first) as a zero padded decimal number.
%W Week number of the year (Monday is first) as a decimal number.
%c Locale’s appropriate date and time representation.
%x Locale’s appropriate date representation.
%X Locale’s appropriate time representation.
%% A literal '%' character.
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Re: Convert Date to yyyymmdd string in field calculator with Python

JoshuaBixby — Fri, 31 May 2019 18:48:05 GMT

It always helps to provide the specific errors and tracebacks you are getting. There are so many possible errors that just saying you are getting an error isn't helpful.

In ArcMap, cursors and the field calculator return date fields as text/unicode, so you have to be aware of that when trying to process the date information. So you may need something like:

(datetime.datetime.strptime( !DateField!,'%m/%d/%Y')).strftime('%Y%m%d')‍

Re: Convert Date to yyyymmdd string in field calculator with Python

NealBanerjee — Sat, 01 Jun 2019 21:16:01 GMT

Hi Joshua - this helps thanks!

I wasnt putting the datetime.datetwice

Re: Convert Date to yyyymmdd string in field calculator with Python

davidround — Sun, 12 Dec 2021 02:20:45 GMT

I made this function for adding a string date field. Hope it helps someone:

def addStringDate(gdbname,tablename,datefieldname):
    arcpy.AddField_management(in_table=gdbname+"/"+tablename, field_name=datefieldname+"_STR", field_type="TEXT", field_precision="", field_scale="", field_length="10", field_alias="", field_is_nullable="NULLABLE", field_is_required="NON_REQUIRED", field_domain="")
    arcpy.CalculateField_management(in_table=gdbname+"/"+tablename, field=datefieldname+"_STR", expression="arcpy.time.ParseDateTimeString( !"+datefieldname+"!).strftime('%Y%m%d')", expression_type="PYTHON", code_block="")‍‍‍

Re: Convert Date to yyyymmdd string in field calculator with Python

JeffDuMez1 — Wed, 12 Jun 2019 17:05:23 GMT

With Field Calculator (python parser) you can convert a string field from a format using YYYYMMDD (example 20190522) to a date field (5/22/2019) using this expression:

(datetime.datetime.strptime( !OwnershipDate!,'%Y%m%d')).strftime('%m/%d/%Y')

My field named OwnershipDate is formatted as a string with values YYYYMMDD, in this example 20190522.

My reply is a bit redundant but after reading though many forum posts, everyone had slightly different requirements so the other examples threw me off. This is for people who want to do what I specifically needed: To calculate a date field from a string field formatted YYYYMMDD. Hope this adds clarity and helps someone!

Re: Convert Date to yyyymmdd string in field calculator with Python

JoshuaBixby — Wed, 12 Jun 2019 17:49:31 GMT

Be aware that cursors and field calculator return actual datetime objects in ArcGIS Pro.

Re: Convert Date to yyyymmdd string in field calculator with Python

DavidTillberg_community — Mon, 14 Mar 2022 12:38:21 GMT

Appears to return strings in Pro python though. Thanks very helpful posts!