Python timedelta() error

Ignition
1

I’m trying to update a session variable sessDateStart with an offset number of days from another variable sessDateEnd using datetime’s timedelta function. When I run this code from a test button I get stuck at the last line (of the snippet) …

	import datetime
	from datetime import timedelta

	system.perspective.print(self.session.custom.sessDateEnd)		# 2020-12-09 12:00:00.000
	system.perspective.print(type(self.session.custom.sessDateEnd))	# class java.util.Date
	d2 = self.session.custom.sessDateEnd
	system.perspective.print(type(d2))								# class java.util.Date
	d = self.session.custom.sessDateDays
	system.perspective.print(d)										# Returns 7.
	system.perspective.print(type(d))								# class org.python.core.PyUnicode
	d1 = d2 + timedelta(days=d)

… with the error message …

[AWT-EventQueue-0] ERROR com.inductiveautomation.ignition.client.util.gui.ErrorUtil - Error running action 'dom.onClick' on subViews/viewMain@D/root/FlexContainer_0/FlexContainer/Button_0: Traceback (most recent call last):
  File "<function:runAction>", line 12, in runAction
  File "C:\Program Files\Inductive Automation\Ignition\user-lib\pylib\datetime.py", line 499, in __new__
    days += weeks*7
TypeError: cannot concatenate 'unicode' and 'int' objects

I’ve searched this forum and the usual StackExchange sites but can’t find my error. Can anyone give me some guidance?

[Ignition 8.1 / Jython 2.7]

2

It means sessDateEnd is a string (unicode is a flavor of string), not java.util.Date. Probably getting that from a bound date entry component.

FWIW, you should avoid jython’s datetime. There be dragons. Use java’s Date and Calendar and related classes instead.

3

The system.date scripting functions should make this easier as well.

2 Likes
4

Thanks, Phil. I’ve seen you recommending this in several posts. I think it’s starting to dawn on me that I just need to use the system.date functions.

	# DateStart = DateEnd - numberOfDays
	self.session.custom.sessDateStart = system.date.addDays(
		self.session.custom.sessDateEnd, 
		- int(self.session.custom.sessDateDays)
	)