Attributeerror: str Object has no attribute 'num_points'

Question

I am trying to create a data collector of an experiment I am doing. So far I have the following code:

in an archive experiments.py has the class:

import csv

class Experimento:
        
       def __init__(self, material: str, num_points: int, time: float=20.0, expType: str='varredura'):
            
            if expType not in ('varredura','ponto fixo'):
                raise ValueError('Tipo de experimento inválido. Selecione entre Varredura ou Ponto Fixo. \n NOTA: não utilize letras maiúsculas!')
            
            self.num_points = num_points
            self.time = time
            self.material = material
            self.expType = expType

And the subclass:

class Ponto_Fixo(Experimento):
    
    def __init__(self, material: str, num_points: int, x: int, z: int, time: float=20.0):
        Experimento.__init__(material, num_points, time, 'ponto fixo')
        self.x = x
        self.z = z
        self.expID = material + ' x' + str(self.x) + ' z' + str(self.z) + ' pt=' + str(num_points)
        
        header = ['data','material','ponto','x','z','contagem','tempo(s)']
        
        csv_title = '\%s.csv' %(self.expID)
        with open('resultados'+ csv_title,'w') as file:
            writer = csv.writer(file)
            writer.writerow(header)

In the main.py, I run this code like this:

import experiments

if __name__ == "__main__":
    material = 'agua+CaCO3'
    expType = 'ponto fixo'
    tempo = 20.0
    num_points = 6
    x = 2
    z = 2

def new_experiment(material, num_points, tempo, x, z, expType):
        
    if expType == 'ponto fixo':
        
        experiments.Ponto_Fixo(material, num_points, x, z, tempo)
        
novo_exp = new_experiment(material, num_points, tempo, x, z, expType)

However, by doing this execution I get the title error

  File "C:\Adam\Doutorado\Laboratorio\TARG\programs\data collection\main.py", line 46, in <module>
    novo_exp = new_experiment(material, num_points, tempo, x, z, expType)

  File "C:\Adam\Doutorado\Laboratorio\TARG\programs\data collection\main.py", line 37, in new_experiment
    experiments.Ponto_Fixo(material, num_points, x, z, tempo)

  File "C:\Adam\Doutorado\Laboratorio\TARG\programs\data collection\experiments.py", line 113, in __init__
    Experimento.__init__(material, num_points, time, 'ponto fixo')

  File "C:\Adam\Doutorado\Laboratorio\TARG\programs\data collection\experiments.py", line 37, in __init__
    self.num_points = num_points

AttributeError: 'str' object has no attribute 'num_points'

The line that the program accuses the error is this (which is within the Experiment class):

self.num_points = num_points

Also, the line that changes the type of the variable num_point of int for str is after this line of error. Therefore, I am not able to see where and why is taking place the change of type of int for str in the num_point.

Can anyone shed a light? Thank you

Answer 1

I believe the goal is to access the "father" class, so change:

Experimento.__init__(material, num_points, time, 'ponto fixo')

For super(), thus:

super().__init__(material, num_points, time, 'ponto fixo')

If it’s Python 2 you’ll have to use it like this:

super(Ponto_Fixo, self).__init__(material, num_points, time, 'ponto fixo')

Official documentation: https://docs.python.org/3/library/functions.html#super, that’s where it’s ideal to start learning, syntax, language features and native Apis.