Class level variables in Python

mackstann mack at incise.org
Thu Aug 28 01:59:32 CEST 2003


On Wed, Aug 27, 2003 at 04:43:03PM -0700, Brian Munroe wrote:
> I was wondering if someone could explain if there is any difference
> between initalizing your object attributes up in the __init__
> constructor or setting them up as (I am guessing at the name here)
> object level variables (like z)

Generally, if something is more or less constant, I make it a class
variable.  If its value depends on the arguments passed to __init__, or
if it is something like a network connection, file operation, etc, then
it goes in __init__.

class Foo:
  specialSequence = "blahblah"

  def __init__(self, filename):
    self.fp = file(filename, "r")
    if self.fp.read(8) == self.specialSequence:
      # .. do something .. 

specialSequence has no reason to be in the constructor, but fp does.  I
suppose that's a good guideline - if you can't think of a reason for it
to be in __init__, then don't put it there.

-- 
m a c k s t a n n  mack @ incise.org  http://incise.org
The four building blocks of the universe are fire, water, gravel and vinyl.
		-- Dave Barry





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