Sorry this will be a very basic question, I am learning python.
I went through a coding exercise to calculate bmi and went for a straightforward way:
def bmi(weight, height):
bmi = weight / height ** 2
if bmi <= 18.5:
return "Underweight"
elif bmi <= 25:
return "Normal"
elif bmi <= 30:
return "Overweight"
else:
return "Obese"
However, in the exercise solutions I also see this one:
def bmi(weight, height):
b = weight / height ** 2
return ['Underweight', 'Normal', 'Overweight', 'Obese'][(b > 30) + (b > 25) + (b > 18.5)]
I want to understand what this double/back-to-back list is where they’ve got [items][conditions] but I can’t find the name of it to learn about it – what is the name for this? Is it a part of list comprehensions?
>Solution :
observe this line carefully
['Underweight', 'Normal', 'Overweight', 'Obese'][(b > 30) + (b > 25) + (b > 18.5)]
Above is line is actually list indexing [(b > 30) + (b > 25) + (b > 18.5)] this gives the index of the list ['Underweight', 'Normal', 'Overweight', 'Obese']. Let us say b > 30 then it satisfies all the three conditions (b > 30) + (b > 25) + (b > 18.5) the equivalent boolean value of each condition is 1 making the sum 3 and returns index 3 which is Obese. Similarly it works for other conditions.