Flask instanciation app = Flask()

Question

I intentionally removed name in app = Flask(name) and I get this error:

Traceback (most recent call last):
    File "routes.py", line 4, in <module>
        app = Flask() 
TypeError: __init__() takes at least 2 arguments (1 given)

this is my code from nettuts and here is my code:

from flask import Flask, render_template

app = Flask() 

@app.route('/')
def home():
    return render_template('home.html')

@app.route('/about')
def about():
    return render_template('about.html')


if __name__ == '__main__':
    app.run(debug=True)

My question is: Where is this init method that takes at least 2 arguments?

Answer 1

If you understand the concept of class and objects, then __init__ is the constructor which initializes an instance of the class. In this case, the class is Flask and when you do the following, you are initializing the instance of a Flask object:

app = Flask(__name__) 

Now your question, "Where is this init method that takes at least 2 arguments?"

That can be explained as per the definition below that defines the constructor in the code.

def __init__(self, import_name, static_path=None, static_url_path=None,
                 static_folder='static', template_folder='templates',
                 instance_path=None, instance_relative_config=False):

If you see above, self and import name is the required parameter and rest are all defaulted or not required. The self is needed by Python even though you can name it anything else. read this blog by creator of python himself for why http://neopythonic.blogspot.com/2008/10/why-explicit-self-has-to-stay.html