python - Readable try except handling with calculations -

i have program have quite lot of calculations need do, input can incomplete (so cannot calculate results), in fine, gives issues readability of code:

def try_calc():     = {'1': 100, '2': 200, '3': 0, '4': -1, '5': none, '6': 'a'}     try:         a['10'] = float(a['1'] * a['2'])     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         a['10'] = none     try:         a['11'] = float(a['1'] * a['5'])     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         a['11'] = none     try:         a['12'] = float(a['1'] * a['6'])     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         a['12'] = none     try:         a['13'] = float(a['1'] / a['2'])     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         a['13'] = none     try:         a['14'] = float(a['1'] / a['3'])     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         a['14'] = none     try:         a['15'] = float((a['1'] * a['2']) / (a['3'] * a['4']))     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         a['15'] = none     return  in [39]: %timeit try_calc() 100000 loops, best of 3: 11 µs per loop 

so works well, high performing unreadable. came 2 other methods handle this. 1: use specialized functions handle issues internally

import operator def div(list_of_arguments):     try:         result = float(reduce(operator.div, list_of_arguments, 1))     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         result = none     return result  def mul(list_of_arguments):     try:         result = float(reduce(operator.mul, list_of_arguments, 1))     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         result = none     return result  def add(list_of_arguments):     try:         result = float(reduce(operator.add, list_of_arguments, 1))     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         result = none     return result  def try_calc2():     = {'1': 100, '2': 200, '3': 0, '4': -1, '5': none, '6': 'a'}     a['10'] = mul([a['1'], a['2']])     a['11'] = mul([a['1'], a['5']])     a['12'] = mul([a['1'], a['6']])     a['13'] = div([a['1'], a['2']])     a['14'] = div([a['1'], a['3']])     a['15'] = div([         mul([a['1'], a['2']]),          mul([a['3'], a['4']])         ])     return  in [40]: %timeit try_calc2() 10000 loops, best of 3: 20.3 µs per loop 

twice slow , still not readable honest. option 2: encapsulate inside eval statements

def eval_catcher(term):     try:         result = float(eval(term))     except (zerodivisionerror, keyerror, typeerror, valueerror) e:         result = none     return result  def try_calc3():     = {'1': 100, '2': 200, '3': 0, '4': -1, '5': none, '6': 'a'}     a['10'] = eval_catcher("a['1'] * a['2']")     a['11'] = eval_catcher("a['1'] * a['5']")     a['12'] = eval_catcher("a['1'] * a['6']")     a['13'] = eval_catcher("a['1'] / a['2']")     a['14'] = eval_catcher("a['1'] / a['3']")     a['15'] = eval_catcher("(a['1'] * a['2']) / (a['3'] * a['4'])")     return  in [41]: %timeit try_calc3() 10000 loops, best of 3: 130 µs per loop 

so slow (compared other alternatives is), @ same time readable one. aware of issues (keyerror, valueerror) handled pre-processing dictionary ensure availability of keys still leave none (typeerror) , zerodivisionerrors anyway, not see advantage there

my question(s): - missing other options? - crazy trying solve way? - there more pythonic approach? - think best solution , why?

how storing calculations lambdas? can loop through of them, using single try-except block.

def try_calc():     = {'1': 100, '2': 200, '3': 0, '4': -1, '5': none, '6': 'a'}     calculations = {         '10': lambda: float(a['1'] * a['2']),         '11': lambda: float(a['1'] * a['5']),         '12': lambda: float(a['1'] * a['6']),         '13': lambda: float(a['1'] / a['2']),         '14': lambda: float(a['1'] / a['3']),         '15': lambda: float((a['1'] * a['2']) / (a['3'] * a['4']))     }     key, calculation in calculations.iteritems():         try:             a[key] = calculation()         except (zerodivisionerror, keyerror, typeerror, valueerror) e:             a[key] = none 

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by way, don't recommend doing if order of calculations matter, if had in original code:

a['3'] = float(a['1'] * a['2']) a['5'] = float(a['3'] * a['4']) 

since dicts unordered, don't have guarantee first equation execute before second. a['5'] might calculated using new value of a['3'], or might use old value. (this isn't issue calculations in question, since keys 1 through 6 never assigned to, , keys 10 through 15 never used in calculation.)