Why the dictionary element is not working with the max function in python?

Question

While working with a trainer module I used dictionary to store the parameter being observed and the corresponding accuracy of the data for the parameter value. The parameter being the key to the dictionary and the accuracy being the value.

I have used sklearn.metrics tool to calculate the accuracy here. But the result is showing the following behaviour.

def fit(self, X, Y):
    acc={}
    best_b = 0
    for b in range(0, X.shape[1] + 1):
      self.b=b
      Y_Pred = self.predict(X)
      acc[b]=accuracy_score(Y_Pred,Y)
    print(type(acc))
    best_b = max(acc, key=acc.get)
    self.b = best_b
    print("Best b : ", self.b, " with highest accuracy : ", acc[self.b])

Output:

<class 'dict'>
<ipython-input-184-8b55ae4bcee2> in fit(self, X, Y)
     21       acc[b]=accuracy_score(Y_Pred,Y)
     22     print(type(acc))
---> 23     best_b = max(acc, key=acc.get)
     24     self.b = best_b
     25     print("Best b : ", self.b, " with highest accuracy : ", acc[self.b])

TypeError: 'list' object is not callable

Why the dictionary is being treated as list object?

type(acc) is to check the datatype of the acc variable. and max here should return an int64 value with the key corresponding to the maximum accuracy value. — govindkumar, Oct 25 '20 at 07:22
I think this can help : https://stackoverflow.com/questions/268272/getting-key-with-maximum-value-in-dictionary — Olivier Sohn, Oct 25 '20 at 10:26

score 1 · Accepted Answer · answered Oct 25 '20 at 16:25

This use of max on dictionary is valid:

In [1]: acc = {}
In [2]: acc = {'a':1, 'b':3, 'c':2}
In [3]: max(acc, key=acc.get)
Out[3]: 'b'
In [4]: type(max)
Out[4]: builtin_function_or_method

The error suggests that you have redefined max. It is no longer the builtin function, but a list. That's why I keep asking type(max).

In [5]: max=[1,2,3]
In [6]: max(acc, key=acc.get)
Traceback (most recent call last):
  File "<ipython-input-6-d5bdb2afa5ad>", line 1, in <module>
    max(acc, key=acc.get)
TypeError: 'list' object is not callable

In [7]: type(max)
Out[7]: list

Why the dictionary element is not working with the max function in python?

1 Answers1