Python Class and Object coding errors

Question

Problem 1

First I need to create a Person class. Then I must write a status method in the Person class. The method should call the bmi() method and, based on the returned result, return the person's status as a string, using the following rules:

BMI               Status
< 18.5            Underweight
>= 18.5 and < 25  Normal
>= 25 and < 30    Overweight
>= 30             Obese

This I was able to do. And now, I am to do the following:

Problem 2

Add after the class a function read_people(csv_filename) that takes as a parameter the name of a CSV file of person data and returns a list of Person objects, one for each line in the input file (and in the same order). The function should only require 7 - 10 lines, excluding comments and blank lines. The maximum function length is set to 10 statements for this question.

The input CSV file will contain 4 columns:

a name (not containing a comma)
an integer age (in years)
a float weight (in kg)
a float height (in metres)

For example, the file people1.csv used in the example below contains the following:

Rolly Polly,47,148.8,1.67
Rosie Donell,23,89.4,1.82
Rambo Stallone,19,59,2.0
Sharon Stone,14,50,1.6
Arnold Shwarnegger,70,59.2,1.65

Test Case

persons = read_people("people1.csv")
for person in persons:
    print(person)

Expected Result

Roly Polly (47) has a bmi of 53.35. Their status is Obese.
Rosie Donell (23) has a bmi of 26.99. Their status is Overweight.
Rambo Stallone (19) has a bmi of 14.75. Their status is Underweight.
Sharon Stone (14) has a bmi of 19.53. Their status is Normal.
Arnold Shwarnegger (70) has a bmi of 21.74. Their status is Normal.

I tried the following code (and FAILED)

"""File for creating Person objects"""

class Person:
    """Defines a Person class, suitable for use in a hospital context.
        Methods: bmi()
    """

    def __init__(self, name, age, weight, height):
        """Creates a new Person object with the specified name, age, weight
           and height"""
        self.name = name
        self.age = age
        self.weight = weight
        self.height = height

    def bmi(self):
        """Returns the body mass index of the person"""
        return self.weight / (self.height * self.height)

    def status(self):
        """dsjhf dsfkj"""
        status = ""
        bmi = Person.bmi(self)
        if bmi < 18.5:
            status = "Underweight"
        if bmi >= 18.5 and bmi < 25:
            status = "Normal"
        if bmi >= 25 and bmi < 30:
            status = "Overweight"
        if bmi >= 30:
            status = "Obese"
        return status

    def __str__(self):
        """outputs data"""
        ans1 = Person.bmi(self)
        ans2 = Person.status(self)
        answer = "{0} ({1}) has a bmi of {2:.02f}. Their status is {3}."
        return answer.format(self.name, self.age, ans1, ans2)

    def read_people(csv_filename):
        """reads file and sorts it then runs through a class"""
        lst = []
        final = []
        file = open(csv_filename, 'r')

        for row in file:
            lst.append(row)
        return lst

    persons = read_people("people1.csv")
    for person in persons:
        print(person)

My Output:

Traceback (most recent call last):
  File "C:/Users/Jason/untitled-2.py", line 61, in <module>
    for person in persons:
builtins.TypeError: 'NoneType' object is not iterable

Problem 3

As if that wasnt enough, now, I need to add a new function filter_people(people, status) that takes a list of people and a "status" string and returns a new list containing just the people from the original list whose health status equals the status parameter. Note that the function is a global function, not a method of the class Person.

The function filter_people(people, status) should only be about 6 lines of code, excluding comments. The maximum function length is set to 10 statements, as for the previous question.

Test

persons = read_people("people1.csv")
for status in ['Underweight', 'Normal', 'Overweight', 'Obese']:
    persons_with_status = filter_people(persons, status)
    print("People who are {}:".format(status))
    for person in persons_with_status:
        print(person)
    print()

Expected Result:

People who are Underweight:
Rambo Stallone (19) has a bmi of 14.75. Their status is Underweight.

People who are Normal:
Sharon Stone (14) has a bmi of 19.53. Their status is Normal.
Arnold Shwarnegger (70) has a bmi of 21.74. Their status is Normal.

People who are Overweight:
Rosie Donell (23) has a bmi of 26.99. Their status is Overweight.

People who are Obese:
Roly Polly (47) has a bmi of 53.35. Their status is Obese.

Where am I going wrong. I keep getting the following error:

builtins.TypeError: 'NoneType' object is not iterable

I need help with Problem 2 and Problem 3. Help!!!

is read_people supposed to return something...? because it doesn't seem to — Eagterrian Knight
– Eagterrian Knight, Commented Oct 5, 2018 at 12:47
BTW, Stack Exchange questions are supposed to contain one question per question. That makes them more useful for future readers. — PM 2Ring
– PM 2Ring, Commented Oct 5, 2018 at 13:03

C.med · Accepted Answer · 2018-10-05 12:57:21Z

2

def read_people(csv_filename):
    """reads file and sorts it then runs through a class"""
    lst = []
    final = []
    file = open(csv_filename, 'r')

    for row in file:
        print(row)
        lst.append(row)

You should return your list at the end of your function

edited Oct 5, 2018 at 12:57

answered Oct 5, 2018 at 12:50

C.med

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3 Comments

C.med Over a year ago

Yes, I think so ;)

C.med Over a year ago

can you add a print to show what contains row before your append?

C.med Over a year ago

@PM 2Ring was right your function is not in the appropriate place, check his answer

PM 2Ring · Accepted Answer · 2018-10-05 13:21:11Z

The read_people function should not be defined inside the Person class. It's a separate function that creates a list of Person instances from the file data, and then returns that list. Your read_people doesn't parse the file data, it doesn't create a Person from that data, and it doesn't return the list.

Here's a repaired version. To make my code self-contained, I read the file data from a list of strings, but it's easy to change it back to reading from the actual CSV file.

# A fake file
file = '''\
Rolly Polly,47,148.8,1.67
Rosie Donell,23,89.4,1.82
Rambo Stallone,19,59,2.0
Sharon Stone,14,50,1.6
Arnold Shwarnegger,70,59.2,1.65
'''.splitlines()


class Person:
    """Defines a Person class, suitable for use in a hospital context.
        Methods: bmi(), status()
    """
    def __init__(self, name, age, weight, height):
        """ Create a new Person object with the specified
            name, age, weight and height
        """
        self.name = name
        self.age = age
        self.weight = weight
        self.height = height

    def bmi(self):
        """ Return the body mass index of the person """
        return self.weight / (self.height * self.height)

    def status(self):
        """ Determine status """
        bmi = self.bmi()
        if bmi < 18.5:
            status = "Underweight"
        elif 18.5 <= bmi < 25:
            status = "Normal"
        elif 25 <= bmi < 30:
            status = "Overweight"
        elif bmi >= 30:
            status = "Obese"
        return status

    def __str__(self):
        """ Output data """
        answer = "{0} ({1}) has a bmi of {2:.02f}. Their status is {3}."
        return answer.format(self.name, self.age, self.bmi(), self.status())

def read_people(csv_filename):
    """reads file and sorts it then runs through a class"""
    lst = []
    #file = open(csv_filename, 'r')
    for row in file:
        name, age, weight, height = row.split(',')
        lst.append(Person(name, int(age), float(weight), float(height)))
    #file.close()
    return lst

persons = read_people("people1.csv")
for person in persons:
    print(person)

output

Rolly Polly (47) has a bmi of 53.35. Their status is Obese.
Rosie Donell (23) has a bmi of 26.99. Their status is Overweight.
Rambo Stallone (19) has a bmi of 14.75. Their status is Underweight.
Sharon Stone (14) has a bmi of 19.53. Their status is Normal.
Arnold Shwarnegger (70) has a bmi of 21.74. Their status is Normal.

Rather than using name, age, weight, height = row.split(',') to parse the file data, it would be better to use the standard csv module, but I suspect that for this assignment you aren't allowed to do that.

Your code for the Person class was mostly ok, but I've made a few minor adjustments to it.

Now see if you can figure out Problem 3. ;) If you get stuck, please ask a new question (you can link it to this question if you want).

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