SchoolTool Gradebook

Rounding edge cases for averages

Bug #1372624 reported by Douglas Cerna on 2014-09-22

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	SchoolTool Gradebook	New	Undecided	Douglas Cerna

We use string formatting for printing averages:

"%.1f" % average

We store grades as decimals and in some cases this produces a rounding issue:

>>> average = Decimal('6.85')
>>> '%.1f' % average
'6.8'

We need to use decimal's rounding options for this.

This applies to the section gradebook as well as the report card.

Douglas Cerna (replaceafill) on 2014-09-22

Changed in schooltool.gradebook:
assignee:	nobody → Douglas Cerna (replaceafill)

Revision history for this message

Gediminas Paulauskas (menesis) wrote on 2014-09-22:

The problem is default decimal rounding setting of ROUND_HALF_EVEN (on 5 round to closest even number).

>>> print '{:.2}'.format(decimal.Decimal('6.75'))
6.8

>>> average = decimal.Decimal('6.85')

>>> print '{:.1f}'.format(average)
6.8

>>> ctx = decimal.Context(rounding=decimal.ROUND_HALF_UP)

>>> with decimal.localcontext(ctx):
print '{:.1f}'.format(average)
...
6.9

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