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Question

I have created a calculator that determines the tax for a given income. I use a for-loop to produce this output. I need to write a piece of code that extracts the top rate that applies to income, and I have been unable to do this. Right now, my calculator just returns the last tax rate in the loop, which for my print statement is .10. I need it to return .15 in this case.

#import TaxReturn class
from TaxReturn  import TaxReturn
#Define tax brackets for each filing status
class TaxCalculator:

   def __init__(self):
     self.brackets = {
        'single': (
            (0, 0.10),
            (8025, 0.15),
            (32550, 0.25),
            (78850, 0.28),
            (164550, 0.33),
            (357700, 0.35),
            (371815, 0.396)
            ),
        'married_jointly': (
            (0, 0.10),
            (16050, 0.15),
            (65100, 0.25),
            (131450, 0.28),
            (200300, 0.33),
            (357700, 0.35),
            (418292, 0.396)
            ),
        'married_separately': (
            (0, 0.10),
            (8025, 0.15),
            (32550, 0.25),
            (65725, 0.28),
            (100150, 0.33),
            (178850, 0.35),
            (209146, 0.396)
            ),
        'head_of_household': (
            (0, 0.10),
            (11450, 0.15),
            (43650, 0.25),
            (112650, 0.28),
            (182400, 0.33),
            (357700, 0.35),
            (395054, 0.396)
            )
                            }

  #calculate tax liability
   def TaxLiability (self, taxReturn):
      tax_liability = 0
      top_tax_rate = 0
      taxable_income = taxReturn.taxComp.taxable_inc
      for bracket in reversed(self.brackets[taxReturn.taxComp.filing_status]):
          if taxable_income > bracket[0]:
              tax_liability += (taxable_income - bracket[0]) * bracket[1]
              taxable_income -= taxable_income - bracket[0]             
              top_tax_rate = bracket[1]

      #round tax to two decimal places
      tax_liability = round(tax_liability, 2)
      return tax_liability, top_tax_rate

#assign name to TaxReturn class and update TaxReturn 
tr = TaxReturn()
tc = TaxCalculator()
tax_liability = tr.taxComp.inc_tax_before_credits 
top_tax_rate = tr.Misc.top_tax_rate
#test statements, output income tax before credits
tr.taxComp.filing_status = 'single'
tr.taxComp.taxable_inc = 25000
print('Unit Test for Tax Calulcator Module:')
print('///////////////////////////////////////////////////////////')
print("Single: ") 
print("Income tax before credits: " + str(tc.TaxLiability(tr)[0])) 
print("Top marginal rate: " + str(tc.TaxLiability(tr)[1]))

Answer 1

Simply break once you've found the tax rate. This allows you to escape from the loop early, once your if condition has been met.

def TaxLiability (self, taxReturn):
  tax_liability = 0
  top_tax_rate = 0
  taxable_income = taxReturn.taxComp.taxable_inc
  for bracket in reversed(self.brackets[taxReturn.taxComp.filing_status]):
      if taxable_income > bracket[0]:
          tax_liability += (taxable_income - bracket[0]) * bracket[1]
          taxable_income -= taxable_income - bracket[0]             
          top_tax_rate = bracket[1]
          break

  #round tax to two decimal places
  tax_liability = round(tax_liability, 2)
  return tax_liability, top_tax_rate

You can also take a look at the documentation on break clauses within a loop.