Python: list containing members of a class

Question

nop = 0
patron = list
def createnew(firstname, lastname, phone, age, gender):
    name = (lastname.lower() + ", " + firstname.lower())
    patron.append(patrons(name, phone, age, gender))
    nop += 1
class patrons():
number = 1

    def __init__(self, name, phone, age, gender):
        self.name = name
        self.phone = phone
        self.age = age
        self.gender = gender

There's a couple of parts of my code for a program that holds information about library patrons. What I want to do is store all the members of the class (patrons) in a list (patron), I know the names are a little confusing, I wasn't really thinking, sorry about that. The problem which I am encountering is that when I run the createnew function, I receive an error which says "descriptor 'append' requires a 'list' object but received a 'patrons'" I was under the impression that I could store class objects in a list. Am I unable to do this? If I can do it, what do I have to change?

unutbu · Answer 1 · 2014-01-08T22:10:40.450

patron = list should probably be patron = list():

Calling list.append(1) reproduces an error similar to the one you mention:

In [1]: list.append(1)
TypeError: descriptor 'append' requires a 'list' object but received a 'int'

To understand the meaning of the error message, you might start by reading about how methods are descriptors. Also note that in Python2 unbound methods such as list.append must be called with an instance of the calling class (e.g. list). But that is mostly irrelevant to fixing your problem unless you are curious about the nature of the error.

patron = list makes patron equal to the built-in class list. patron = list() makes patron an instance of the class list.

score 1 · Accepted Answer · edited May 23 '17 at 12:21

1

you should setup patron as

patron = list()

Unrelatedly, nop += 1 will throw an UnboundLocalError. Add global nop inside createnew More info here

edited May 23 '17 at 12:21

Community

1
1

answered Jan 08 '14 at 22:05

mhlester

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Thanks, everyone got it, but you also worked out the second issue. Thanks to everyone for all the help – user2832964 Jan 08 '14 at 22:16

score 1 · Answer 3 · answered Jan 08 '14 at 22:08

As said before, list should be list() and you should give nop as an argument:

nop = 0
patron = list()
def createnew(firstname, lastname, phone, age, gender, nop):
    name = (lastname.lower() + ", " + firstname.lower())
    patron.append(patrons(name, phone, age, gender))
    nop += 1

class patrons():
    number = 1
    def __init__(self, name, phone, age, gender):
        self.name = name
        self.phone = phone
        self.age = age
        self.gender = gender

nop being an integer is immutable, meaning it gets reassigned when you call `nop += 1` and does not mutate the global variable — mhlester, Jan 08 '14 at 22:09

Python: list containing members of a class

3 Answers3