DEV Community

HHMathewChan
HHMathewChan

Posted on • Originally published at rebirthwithcode.tech

Python Exercise 14: sum of fractions

#beginners #python #challenge #devjournal

Question

  • Create a function that takes a list containing nested lists as an argument.
  • Each sublist has 2 elements.
  • The first element is the numerator and the second element is the denominator.
  • Return the sum of the fractions rounded to the nearest whole number.

Examples 

sum_fractions([[18, 13], [4, 5]]) ➞ 2 sum_fractions([[36, 4], [22, 60]]) ➞ 9 sum_fractions([[11, 2], [3, 4], [5, 4], [21, 11], [12, 6]]) ➞ 11
Enter fullscreen mode Exit fullscreen mode

My solution

  • algorithm 
>>separate the sublist in the nested list iterate over the nested list >>separate elementes in the sublist iterate over the sublist >>for each sublist, calculate the fraction set the first element to the numerator set the second element is the denominator store the result to a variable called:total >>return the variable total
Enter fullscreen mode Exit fullscreen mode
  • code 
def sum_fractions(nested_list:list): total = 0 list_of_sum = list() for sublist in nested_list: division = int(sublist[0]) / int(sublist [1]) total += division return round(total)
Enter fullscreen mode Exit fullscreen mode

Other solution

  • unpacking the sublist by multiple assignment
    • i.e. use numerator for the first element of the sublist
      • use denominator for the second element of the sublist 
def sum_fractions(lst): return round(sum(numerator/ denominator for numerator, denominator in lst))
Enter fullscreen mode Exit fullscreen mode

My reflection

  • I have learned using multiple assignment instead of using index to access the value of a list.

Credit

Top comments (2)

Collapse
 
mellen profile image
Matt Ellen-Tsivintzeli •

Fun little problem! Here's my solution, using the way we were taught to add fractions at school 😋 (I added in fraction reduction for extra spice!)

from math import gcd def reduce_fraction(fraction): hcf = gcd(fraction[0], fraction[1]) return [fraction[0]//hcf, fraction[1]//hcf] def sum_of_fractions(fractions): total = fractions.pop() while len(fractions) > 0: next = fractions.pop() bottom = total[1] * next[1] topLeft = next[1] * total[0]; topRight = next[0] * total[1] total = [topLeft + topRight, bottom] return reduce_fraction(total) test = [[11, 2], [3, 4], [5, 4], [21, 11], [12, 6]] fraction_sum = sum_of_fractions(test[:]) result = round(fraction_sum[0]/fraction_sum[1]) print(f'The sum of {test} fractions is {fraction_sum}, which is {result} to the nearest integer')
Enter fullscreen mode Exit fullscreen mode
Collapse
 
mathewchan profile image
HHMathewChan •

Interesting method, just learn a syntax(test[:]) from you. Also good exercise for me to read long code from others.