Question

I have written this code:

    class component(object):

      def __init__(self,
                   name = None,
                   height = None,                 
                   width = None):

        self.name = name        
        self.height = height
        self.width = width

class system(object):

      def __init__(self,
                   name = None,                 
                   lines = None,
                   *component):

        self.name = name
        self.component = component

        if lines is None:
                self.lines = []
        else:
                            self.lines = lines

      def writeTOFile(self,
                      *component):
        self.component = component

        line =" "
        self.lines.append(line)

        line= "#----------------------------------------- SYSTEM ---------------------------------------#" 
        self.lines.append(line)


Component1 = component ( name = 'C1',
                         height = 500,
                         width = 400)
Component2 = component ( name = 'C2',
                         height = 600,
                         width = 700)

system1 = system(Component1, Component2)
system1.writeTOFile(Component1, Component2)

and I get the error :

  Traceback (most recent call last):
  File "C:\Python27\Work\trial2.py", line 46, in <module>
    system1.writeTOFile(Component1, Component2)
  File "C:\Python27\Work\trial2.py", line 32, in writeTOFile
    self.lines.append(line)
AttributeError: 'component' object has no attribute 'append'

And I don’t really know how to fix it.

Also is there a way for defining my system1 as system(Component) where component = [Component1, Component2, …Componentn] ?

Thanks in adavance

Answer 1

You’ve got things out of order in your __init__:

  def __init__(self, *component, **kwargs):

    self.name = kwargs.get('name')
    self.component = component

    self.lines = kwargs.get('lines', [])

Will work. You need lines and name to be after the * item that collects the component.

In Python 2, you can’t then have named attributes after a *, so you need to instead use **kwargs and get('name') and get('lines') from the kwargs.

get just returns None if you don’t supply a default, so you’ll get self.name = None here. If you want to specify a default name, you can do

    self.name = kwargs.get('name', 'defaultname')

like I did for lines.