CODEWITHSUNDEEP
pythonattributes
Pratyush Dhanuka
Pratyush Dhanuka

Reputation: 1445

AttributeError: can't set attribute in python

Here is my code

N = namedtuple("N", ['ind', 'set', 'v'])
def solve():
    items=[]
    stack=[]
    R = set(range(0,8))
    for i in range(0,8):
        items.append(N(i,R,8))      
        stack.append(N(0,R-set(range(0,1)),i))
    while(len(stack)>0): 
        node = stack.pop()
        print node
        print items[node.ind]   
        items[node.ind].v = node.v

In the last line I cant set the items[node.ind].v value to node.v as I want, and am getting the error

"AttributeError: can't set attribute"

I don't know what's wrong but it must be something based on syntax as using statements like node.v+=1 is also showing same error. I'm new to Python, so please suggest a way to make the above change possible.

Upvotes: 112

Views: 297096

Answers (7)

JGFMK
JGFMK

Reputation: 8904

For anyone else Googling in to this message, I got this error due to a copy/paste error. The def method for the setter didn't exist with the correct name. For example:

def __init__(self,a):
     self.a = a

...

@property
def a(self):
    return self._a
@a.setter
def b(self, value): # Should have used a(self,value):
    self._a = value

Upvotes: -2

Mahsa Yazdani
Mahsa Yazdani

Reputation: 111

In addition to this answer that Azmisov provided, adding a setter would solve the problem:

class Test:
    def __init__(self):
        self._attr = "original value"
        # This will trigger an error...
        self.attr = "new value"

    @property
    def attr(self):
        return self._attr

    @attr.setter
    def attr(self, value):
        self._attr = value


Test()

Upvotes: 0

jonrsharpe
jonrsharpe

Reputation: 121966

namedtuples are immutable, just like standard tuples. You have two choices:

  1. Use a different data structure, e.g. a class (or just a dictionary); or
  2. Instead of updating the structure, replace it.

The former would look like:

class N(object):

    def __init__(self, ind, set, v):
        self.ind = ind
        self.set = set
        self.v = v

And the latter:

item = items[node.ind]
items[node.ind] = N(item.ind, item.set, node.v)

If you want the latter, Ignacio's answer does the same thing more neatly using baked-in functionality.

Upvotes: 75

Hannes Landeholm
Hannes Landeholm

Reputation: 1629

I came across this when I incorrectly mixed dataclass and NamedTuple. Posting this here to potentially save someone from tearing out their hair.

@dataclasses.dataclass
class Foo(typing.NamedTuple):
    bar: str

Upvotes: 1

Matt Yoon
Matt Yoon

Reputation: 446

This error can be triggered if you try to redefine a member variable that is already defined in the class you inherited.

from pytorch_lightning import LightningModule

class Seq2SeqModel(LightningModule):
    def __init__(self, tokenizer, bart, hparams):
        super().__init__()
        self.tokenizer = tokenizer
        self.bart: BartForConditionalGeneration = bart
        self.hparams = hparams  # This triggers the error
        # Changing above line to below removes the error
        # self.hp = hparams

As I was new to PyTorch and PyTorch Lightning, I did not know the LightningModule already had a member variable named self.hparams. As I tried to overwrite it in my code, it caused AttributeError: can't set attribute.

Just simply renaming my variable from self.hparams to something else removed the error.

Not the problem in the OP's question, but I'm putting it here to help any searching for the error message directly

Upvotes: 4

Azmisov
Azmisov

Reputation: 7253

For those searching this error, another thing that can trigger AtributeError: can't set attribute is if you try to set a decorated @property that has no setter method. Not the problem in the OP's question, but I'm putting it here to help any searching for the error message directly. (if you don't like it, go edit the question's title :)

class Test:
    def __init__(self):
        self._attr = "original value"
        # This will trigger an error...
        self.attr = "new value"
    @property
    def attr(self):
        return self._attr

Test()

Upvotes: 153

Ignacio Vazquez-Abrams
Ignacio Vazquez-Abrams

Reputation: 798546

items[node.ind] = items[node.ind]._replace(v=node.v)

(Note: Don't be discouraged to use this solution because of the leading underscore in the function _replace. Specifically for namedtuple some functions have leading underscore which is not for indicating they are meant to be "private")

Upvotes: 85

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