To get current day :
current_day = datetime.today().strftime('%A') # 'Wednesday'
and for comparing the selection field see my below code.

for cal in attendance.employee_id.resource_calendar_id.attendance_ids.filtered(lambda line: dict(line._fields['dayofweek'].selection).get(line.dayofweek) == current_day and line.day_period == 'morning'):

Here,
'line' is the object like self
'dayofweek' is the selection field.
like this you can compare your selection field key with other variable.