Input superclass variables in Python

Question

I'm building a web crawler with Python. I created a parent class to save the user and the password, that I'd like to be inputed via keyboard.

The parent class looks like this:

class ParentCrawler(object):
def __init__(self):
    """Saves the user and the password"""
    self.user = input("Email: ")
    self.password = getpass.getpass("Password: ")

Then I created a subclass of that parent class with the idea of running parallel instances of it to make the crawling faster. But everytime I create a new object of the child class, I'm asked to input user and pass again, like in the pic below, and that's not what I want.

When a child object is created...

I know I could just hard code my user and pass into the parent class constructor method, but I'd like to know how to input them manually every time the program runned.

Answer 1

Th __init__ method of a class will be run every time you create a new instance. Since this values are needed just once, and you don't need different values for them for each instance, it makes little sense for their values to be requested inside the class initialiser, or other method.

Moreover, if your classes have nothing to do with user interaction on the terminal, there is no reason to hardcode this user interaction in the class code - if you make modifications to your program that will use the same class, and get this information from a configuration file, or from a POSTed web form, for example, you won't be able to use these classes in this way.

There is nothing wrong to pass the credentials as mandatory values when instantiating a class. To continue development and use of your program using it interactivelly at the terminal, you can create a simple function that will request these input data, and return them -

NUM_WORKERS = 4


def get_credentials():
    user = input("Email: ")
    password = getpass.getpass("Password: ")
    return user, password

def main():
    workers = []
    user, password = get_credentials()
    for i in range(NUM_WORKERS):
         worker = Crawler(user, password)
         workers.append(worker)
         worker.start()
    ...


class Crawler:
     def __init__(self, user, password):
           ...