python setattr无限递归,在python中使用setattr（）

I am looking for someone to explain the basics of how to use, and not use setattr().

My problem arose trying to use one class method/function to return data that is then put in another method/function. Perhaps a simpler approach would be much better in this case, but I’m trying to understand how classes work/are used. This problem seems to hinge on setattr(), and this is my attempt to make a fairly simple use of this.

Though it’s not quite the same problem, I was following Python The Hard Way, ex42—the while loop @ lines 18-41.

I tried writing an \__init__(), and using getattr() instead, thinking perhaps something needed to be in the class’ namespace, but this doesn’t seem to help.

#! /bin/python2.6

class HolyGrail(object):

def __init__(self):

self.start = ‘start_at_init’

# function definition in question:

# TypeError: ‘str’ object is not callable

def run_it(self):

start = setattr(self, ‘name’, ‘get_thing’)

start = self.name

# Something wrong here?

value_returned = start() #I believe this == self.get_thing()

use_it(value_returned)

“””

# alternate function definitions

# NameError: global name ‘start’ is not defined

def __init__(self):

self.start = ‘get_thing’

def run_it(self):

go_do_it = getattr(self, start)

first_output = go_do_it()

use_it(first_output)

“””

def get_thing(self):

return “The Knights Who Say … Ni!”

def use_it(self, x):

print x

print “We want a shrubbery!”

my_instance = HolyGrail()

my_instance.run_it()

@Karl Knechtel, @Amber , @Chris Morgan thanks for your help.

I think I can now explain my own answer! This required a better grasp of self as an object for me. It’s an instance name that gets tagged up with stuff like attributes.

The class could be a Town, and then.

getattr looks for a house using it’s name so you are ready to call on it soon, and comes up with a different place if you don’t find the house

–With getattr a ‘name’ exists, and you go find it. Makes the step from one function to another dynamic

As a bonus you may have a default value, useful to get a fallback default method–connection failed or something?

setattr builds a house and gives it a name so you can call in on it later.

You could potentially rebuild this house, or go to a particular place if you are unable to find it.

–setattr makes an attribute name and gives, or changes it’s value, to be called on later

Perhaps a user turns sound off, then future methods don’t output any audio.

I could have written my function a number of ways, but there’s no need to change any attributes:

def run_it(self):

yo = getattr(self, ‘get_thing’)

answer = yo()

setattr(self, ‘deal_accepted’, self.use_it) #really ott

no = getattr(self, ‘deal_accepted’)

no(answer)

Properly corrected code:

def run_it(self):

value_returned = self.get_thing()

self.use_it(value_returned)

解决方案

You are setting self.name to the string “get_thing”, not the function get_thing.

If you want self.name to be a function, then you should set it to one:

setattr(self, ‘name’, self.get_thing)

However, that’s completely unnecessary for your other code, because you could just call it directly:

value_returned = self.get_thing()