TypeError : count() takes at least 1 argument (0 given)

user_13314888 0
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i am getting TypeError: count() takes at least 1 argument (0 given).

it would be great if anybody could figure out where i am doing thing wrong. thank you so much in advance.

class CommentsSerializer(serializers.ModelSerializer):
    comment_count = serializers.SerializerMethodField()
    class Meta:
        model = Comments
        fields = [
            "id", "title", "name", "subject", "comment_count",
        ]

    def get_comment_count(self, obj):
        return obj.subject.count()
django-rest-framework list django python
4 Answers

Your implementation does not make sense. I think you are trying to get count of all the Comments object, but here you are trying to count subject, probably that is a string or a list. On them, count works like this:

IN  >> "aaaaa".count('a')
OUT >> 5
IN  >> [1,2,3,4].count(1)
OUT >> 1

Now, to fix your problem, we need to understand what you want to achieve here. If you want to get count of comments for a particular post, then you can try like this:

If you have a model like this:

class Comments(models.Model):
    post = models.ForeignKey(Post)

Then you can take this approach:

def get_comment_count(self, obj):
    return obj.post.comments_set.count()

This is count() function from Django queryset. And obj.post.comments_set will return a queryset(for having a reverse relationship). If you have defined related_name="post_comments"(docs), then it will become obj.post.post_comments.count().

user_26961650

You may check the function description here

It counts the occurrence of an object in a list, so you need to pass an object as a parameter to count() function, and apply this on a list.

Also, it would be better if you give a sample program that you got the error.

user_137933270

count() requires exactly one argument and returns the number of instances of the provided argument in the list.

If you just want to count number of elements in a list, use:

return len(obj.subject)
user_124002140

count requires an argument. It returns the number of instances of a particular item in a list.

    l=[1,2,5,4,5,6,7,10]
    l.count(5)
    2

2 here is the number of 5s in the list.

user_139919310
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