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?

Answer 1

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.

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

Answer 2

you should setup patron as

patron = list()

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

• user2832964: Thanks, everyone got it, but you also worked out the second issue. Thanks to everyone for all the help

Answer 3

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

• mhlester: nop being an integer is immutable, meaning it gets reassigned when you call nop += 1 and does not mutate the global variable