为什么我会收到“浮动 object 不可调用”错误

Question

I'm getting this error in my code:

Test Failed: 'float' object is not callable.

My code is as follows:

import math

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

def std_dev(persons):
    persons_age = [person.age for person in persons]
    mean = float(sum(persons_age) * 1.0)/len(persons)
    length = float(len(persons))
    mean = float(mean(persons))
    total_sum = 0
    for i in range(length):
        total_sum += float(persons_age[i]- mean)**2
    square_root = float((total_sum * 1.0)/length)
    return math.sqrt(square_root)

Answer 1

This simple example reproduces your error:

In [101]: x = 1.23                                                              
In [102]: x()                                                                   
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-102-08f9d0828de0> in <module>
----> 1 x()

TypeError: 'float' object is not callable

That means, some place in your code, you define a variable as a number, float. And then later you use that variable as though it were a function, with ().

The full traceback should identify which line and variable is the problem. But mean is a good guess.

What is this supposed to do?

mean(persons)

There is a numpy.mean function, but not a base Python one.

On an unrelated matter, you don't need all of those calls to float(...) . In Py3, float division is the norm. So there's no harm in leaving integers that way. Normally you only need float if the argument is a string.