Python属性错误-类型对象没有属性

Question

I am writing some code for a project at school. I am reading in a List that I have created as a text file with 5 attributes. This is my class object code:

class studentclass(object):
    def __init__(self,firstname,lastname,classno,correct,mydate):
        self.firstname = firstname
        self.lastname = lastname
        self.classno = classno
        self.correct = correct
        self.mydate = mydate

Later in the program I am using this code to read in the data, sort it and perform some calculations:

myList = [studentclass]
totalnoofrecords = 0
counter = 0

for counter in range(0,totalnoofrecords):
    firstname = myList.firstname[counter]
    lastname = myList.lastname[counter]
    classno = myList.classno[counter]
    correct = myList.correct[counter]
    mydate = myList.mydate[counter]
    newname = myList.firstname[counter +1]
    if newname == firstname:
            grade = grade + studentclass.correct(counter +1)
            nummberofattempts = 2
    newname2 = studentclass.firstname(counter +2)
    if newname2 == firstname:
            grade = grade + studentclass.correct(counter +2)
            nummberofattempts = 3
    mean = grade / numberofattempts

    print ("num ",counter ,"=", myList[counter])

But it does not work. I get the following error message:

AttributeError: 'list' object has no attribute 'firstname'

The error message points to this line of the code:

firstname = myList.firstname[counter]

Hoping that someone call help me please. Thanks

Answer 1

In your code you are referencing mylist.firstname . What is mylist ? It's a list. Does it have a firstname attribute? The error is telling you that it doesn't, and looking at the code you aren't adding that attribute to the list.

Each element of the list has that attribute, however. Perhaps you meant to get the firstname attribute of one of the elements of the list. Maybe the following, perhaps?

for counter in range(0,totalnoofrecords):
    firstname = myList[counter].firstname
    lastname = myList[counter].lastname
    ...

In python, when you get an error like "object X has no attribute Y", you can usually rely on that being a true statement. So, ask youself "why does X not have that attribute?". It's usually either a) you forgot to define that attribute, b) you misspelled the attribute or you misspelled X, or c) X isn't what you think it is.

Answer 2

You have several issues. As Alex S. pointed out, your myList is a List, and specifically it is a list with one element: a class constructor.
I think what you want is something like:

  # assumption: you have textlines, 
  # which is an array of lines of the form firstname,lastname,blah
  myList = [studentclass(*(args.split(",")) for args in textlines]

And then do myList[counter].firstname to get the (counter-th) firstname value