OOP / try except statements in __init__ of class

Question

I want to control the input of the class Webpage. Meaning, I want to be sure that the webpage's link is appropriately provided, e.g. 'http://example.com'.

class Webpage(object):
    def __init__(self, link):
        prefix = ['http', 'https']
        suffix = ['com', 'net']
        try:
            if link.split(':')[0] in prefix and link.split('.')[-1] in suffix:
                self.link = link
        except:
            raise ValueError('Invalid link') 


   def get_link(self):
        '''
        Used to safely access self.link outside of the class

        Returns: self.link
        '''
        return self.link

   def __str__(self):
        return str(self.link)  

However, when I try code:

test_link = Webpage('example.com')

I do not get ValueError, as I would expect. Call of methods:

test_link.get_link()
print(test_lint)

result in

AttributeError: 'Webpage' object has no attribute 'link'

which indicates that try/except worked partially - try did not execute self.link = link, however except statement wasn't executed.

An example:

test_link = Webpage('http://example.com')

works fine with get_link() and print methods of that class.

Will appreciate any hint.

Answer 1

Raising an expection as in your case ValueError is done in the try block and handling of the expection it is done in the except block

For more information please visit Raising Expections in python

class Webpage(object):
    def __init__(self, link):
        prefix = ['http', 'https']
        suffix = ['com', 'net']
        try:
            if link.split(':')[0] in prefix and link.split('.')[-1] in suffix:

                self.link = link
            else:
                raise ValueError('Invalid link')
        except ValueError as exp:
            print("the value error is {}\nthe link specified is {} ".format(exp,link))



    def get_link(self):
        '''
        Used to safely access self.link outside of the class

        Returns: self.link
        '''
        return self.link

    def __str__(self):
        return str(self.link) 

test_link = Webpage('example.com')

Output

the value error is Invalid link
the link specified is example.com

Hope this helps