Python: Create objects of a class dynamically using a string and then refer to them using that same string

Question

I have a python script that reads a configuration file CSV, e.g.

#PV_name, type
motor_temp_1, 15m
tank_pressure_1, 15m
pump_flow_2, 60m
...
variable_X, 24h

The data is then saved on a dictionary:

csv_content = {
    "motor_temp_1": "15m",
    ...
    "variable_x": "24h"
}

The script communicates cyclically with other devices to read the current values of the variables found at csv_content.. For each value, the script should calculate the average and save the average values on a DB. So for instance, I read every 1 second the temperature of motor 1 (motor_temp_1) and save the average temperature for 15 minutes. For this I've written a Class:

class Average:
    def __init__(self, name, type):
        self.name = name
        self.type = type
        self.avg = 0
    def read_sample(self, current_value):
        # code for calculating average across the given time
        return self.avg

How can I dynamically create Instances of the class Average from the strings found in csv_content? And then access their respective read_sample method when reading the values from the external devices?

# Create instances of Average class (QUESTION 1)
for key in csv_content:
    instance_named_after_key_string = Average(key, csv_content[key])
    # so I'm expecting something like:
    # motor_temp_1 = Average("motor_temp_1", "15m")
    # tank_pressure_1 = Average("tank_pressure_1", "15m")
    # etc..

# Script for getting current values every 1 second and letting these values go through their Method for calculating average, the current values are being saved on another dictionary
while True:
    # Communicate with external devices and get current_values
    current_values = {
        "motor_temp_1": 15.23,
        "tank_pressure_1" : -21.1,
         ...
        "variable_x": 0.23
    }
    # calculate average for each of the current_values (QUESTION 2)
    for key in current_values:
        instance_named_after_key_string.read_sample(current_values[key])
        # so I'm expecting something like:
        # motor_temp_1.read_sample(15.23)
        # tank_pressure_1.read_sample(-21.1)
        # etc..
    # Print (Save to DB) every 15 minutes
    if ( fifteen_minutes_have_passed):
        for key in current_values:
            print(instance_named_after_key_string.avg)
    time.sleep(1)

Is this even possible? If not, what can I do to solve my problem?

Glenn Mackintosh · Accepted Answer · 2020-05-05 20:48:36Z

1

Instead of trying to create variables named after the string values that hold the class instance, you could create a dictionary that holds the instances.

The keys to the dictionary would be the strings from the csv content and the value would be the instance of the class Average that you want to correspond to those strings.

answered May 5, 2020 at 20:48

Glenn Mackintosh

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