如何使用字典作为规则，使用pd.apply（）将值分配给数据框

Question

def create_rubric(number, df, col):
"""
First finds all the unique fields then segments them in quintiles.
Uses the quintiles to give ratings to the original data
"""

    sorted_col = df[col].sort_values()
    unique_val = sorted_col.unique()
    unique_cut = pd.qcut(unique_val,number,labels=False)
    unique_dict = {"Items" : unique_val, "Labels" : unique_cut}
    df = pd.DataFrame(unique_dict)
    rubric = {}
    rubric[1] = df[df.Labels == 0]
    rubric[2] = df[df.Labels == 1]
    rubric[3] = df[df.Labels == 2]
    rubric[4] = df[df.Labels == 3]
    rubric[5] = df[df.Labels == 4]
    return rubric

def frequency_star_rating(x, rubric):
"""
Uses rubric to score the rows in the dataframe
"""
    for rate, key in rubric.items():
        if x in key:
            return rate

rubric = create_rubric(5,rfm_report,"ordersCount")
rfm_report["Frequency Rating"] = rfm_report["ordersCount"].apply(frequency_star_rating, rubric)

I've written two functions that should interact with each other. One creates a scoring rubric that ends up in a dictionary and the other should use that dictionary to score rows in a dataframe of about 700,000 rows. For some reason I keep getting the “Series objects are mutable and cannot be hashed” error. I really can't figure out the best way to do this. Did I write the functions wrong?

Answer 1

It would be nice if you could provide a toy dataset so we could run your code quickly and see where the error happens.

The error you are getting is trying to tell you that a pd.Series object cannot be used as the key of a dictionary. The reason is that Python dictionaries are hash tables. So, they only accept hashable data types as the key. For example, strings and integers are hashable, but lists are not. So the following works fine:

fine_dict = {'John': 1, 'Lilly': 2}

While this one will throw a TypeError :

wrong_dict = {['John']: 1, ['Lilly']: 2}

The error will look like this: TypeError: unhashable type: 'list'.

So my hunch is that somewhere in your code, you're trying to use a Series object as the key of a dictionary, which you should not because it's not hashable.