Data type mismatch error

[AmiParadkar]

I have a very simple code,

`import rule_engine
from datetime import datetime

company = {
'name': 'Company name',
"establishmentDate": "2021-04-08"
}
rule = rule_engine.Rule(
'("today()" - "3 months" > establishmentDate)'
)

rule.matches(company)`

but I am getting the following error

Traceback (most recent call last):
File "/Users/Documents/apps/PyCharm/tutorial/test.py", line 9, in
rule = rule_engine.Rule(
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/engine.py", line 578, in init
self.statement = self.parser.parse(text, context)
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/parser.py", line 106, in parse
return result.build()
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/parser.py", line 60, in build
return constructor(*self.args, **self.kwargs)
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/ast.py", line 1041, in build
return cls(context, expression.build()).reduce()
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/parser.py", line 60, in build
return constructor(*self.args, **self.kwargs)
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/ast.py", line 362, in build
return cls(context, type_, left.build(), right.build()).reduce()
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/parser.py", line 60, in build
return constructor(*self.args, **self.kwargs)
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/ast.py", line 362, in build
return cls(context, type_, left.build(), right.build()).reduce()
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/ast.py", line 435, in init
super(SubtractExpression, self).init(*args, **kwargs)
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/ast.py", line 355, in init
self._assert_type_is_compatible(left)
File "/Users/Documents/apps/PyCharm/tutorial/venv/lib/python3.10/site-packages/rule_engine/ast.py", line 369, in _assert_type_is_compatible
raise errors.EvaluationError('data type mismatch')
rule_engine.errors.EvaluationError: data type mismatch

[zeroSteiner]

Give this a try:

import rule_engine
import datetime

company = {
	'name': 'Company name',
	'establishmentDate': datetime.date(2021, 4, 8)
}
rule = rule_engine.Rule('$today - t"P90D" > establishmentDate')
print('matches: ' + repr(rule.matches(company)))

Your original had multiple problems, including:

1. establishmentDate is defined as a string instead of a datetime.date or datetime.datetime instance. You probably want it as one of those so you can run comparisons on it like you're trying to do in your rule.
2. Today is accessed through $today not today(). The rule engine doesn't support functions at this time so there's $today which is today's date and $now which is the current timestamp.
3. Your time delta is 3 months is also a string. That needs to be a TIMEDELTA. Months aren't supported because they don't always have the same number of days, so you probably want to check for 90 days. Rougly, a 3month time period would be defined as t"P90D" which it a timedelta literal consisting of a period containing 90 days.

Hope that helps.

[AmiParadkar]

Thank you for your quick response.