A function that will produce BMI and the category user falls into

Question

I am trying to make a code that calculates the BMI of individuals that the user inputs. Here is where I am stuck, using a second loop the program should traverse the array of body mass indices and call another function that accepts the body mass index(BMI) as a parameter and returns whether the individual is underweight, normal weight or overweight, finally I want to count number of individuals in each category. I keep getting an error typeerror: ‘>’ not supported between instances of ‘str’ and ‘int’ Solution. Honestly I don't even know if I'm doing it right at all to get the out put I want. Thank you for any help.

Below if what I've got:

     individuals = list()
    for i in range((int(input("Please enter the number of individuals you would like calculate BMIs for:")))):
        user = str(input("Please enter the names of the individuals one at a time: "))
        individuals.append(user)
    BMIs = []
    for user in individuals:
        print("Input for", user)
        height = int(input(user + ", in inches, how tall are they? "))
        weight = int(input(user + ", in pounds, how much do they weigh? "))
        BMIs.append(user  + "s, BMI is: " + str(weight * 703/height**2))
    
    for BMI in BMIs:
        if ( BMI <18.5):
            print(BMI, "underweight")
        elif ( BMI >= 18.5 and BMI < 30):
            print(BMI,"normal")
        elif ( BMI >=30):
            print(BMI,"severely overweight")

The title should describe your _problem_, not what kind of thing you were writing when you encountered that problem. (Similarly, a good [mre] is simplified to be the _shortest possible code_ that produces the same problem when run without changes; if you can produce the problem without user input or prompting, you should take the user input and the prompting out of your code before posting). — Charles Duffy, Dec 15 '20 at 00:45

NotAName · Answer 1 · 2020-12-15T01:04:54.143

Here you are appending strings to a list BMIs:

BMIs.append(user  + "s, BMI is: " + str(weight * 703/height**2))

So then when you do a comparison Python throws you an error. What you need to do instead is to use a dictionary:

    BMI = {}  # Create an empty dict here
    for user in individuals:
        print("Input for", user)
        height = int(input(user + ", in inches, how tall are they? "))
        weight = int(input(user + ", in pounds, how much do they weigh? "))
        BMI[user] = weight * 703/height**2

Then you can do comparisons using dictionary values:

    for key, value in BMI.items():
        if BMI[key] < 18.5:
            print(f'{key} with BMI of {value} is underweight')
        elif BMI[key] >= 18.5 and BMI[key] < 30:
            print(f'{key} with BMI of {value} has normal weight.')
        elif BMI[key] >=30:
            print(f'{key} with BMI of {value} is overweight.')

Also, you don't need to use brackets in if statements in Python.

Thank you! Using this works for outputting their categories but it seems I've lost the part where it also outputs their actual BMI along with the category. Is this possible? — PintSized, Dec 15 '20 at 01:02

Konstantinos Zafeiris · Answer 2 · 2020-12-15T00:43:11.687

According to your error you are trying to compare a str(string) variable with an int(integer) one. This is because when you are iteratating through your BMIs list, all your BMI values have the form: "user's, BMI is number"

So the comparison that takes place is: "user's, BMI is number" > int(number) You are comparing a whole string to a number and python doesn't understand this.

You need to parse your string and extract your number and then compare it.

One possible way to do this is: BMI[BMI.rindex(" ")::]

So this loop

for BMI in BMIs:
        if ( BMI <18.5):
            print(BMI, "underweight")
        elif ( BMI >= 18.5 and BMI < 30):
            print(BMI,"normal")
        elif ( BMI >=30):
            print(BMI,"severely overweight")

is transformed to:

for BMI in BMIs:
        if (int(BMI[BMI.rindex(" ")::]) <18.5):
            print(BMI, "underweight")
        elif (int(BMI[BMI.rindex(" ")::]) >= 18.5 and int(BMI[BMI.rindex(" ")::]) < 30):
            print(BMI,"normal")
        elif (int([BMI.rindex(" ")::]) >=30):
            print(BMI,"severely overweight")

The rindex method returns the index of the last occurence of the string parameter inside the string. The string[::] notation is a simple string slice.

Rather than parsing a string isn't it easier to simply not create a string in the first place? — NotAName, Dec 15 '20 at 00:45
Yes I completely agree with you, I simply went along with OP's selection. — Konstantinos Zafeiris, Dec 15 '20 at 00:49

A function that will produce BMI and the category user falls into

2 Answers2