When to use if-else statement or try-except statements during exception handling?

Question

For example, I have this code snippet which does some some HTML parsing for me.

from bs4 import BeautifulSoup

class Parser:
    def __init__(self, html_data=None):
        if html_data:
            self.bs = BeautifulSoup(html_data, 'html.parser')

    def setBS(self, html_data):
        self.bs = BeautifulSoup(html_data, 'html.parser')

    def getLinksByID(self, target_id):
        elements = self.bs.find_all(id=target_id)

        links = []
        for element in elements:
            try:
                links.append(element.find('a')['href'])
            except TypeError:
                pass
        return links

    def getLinksByClass(self, target_class):
        elements = self.bs.find_all(class_=target_class)

        links = []
        for element in elements:
            try:
                links.append(element.find('a')['href'])
            except TypeError:
                pass
        return links

I am having problem of deciding when to use a Try-Except statements instead of If-Else statements and vice versa when handling exceptions.

For example instead of doing this

   def __init__(self, html_data=None):
        if html_data:
            self.bs = BeautifulSoup(html_data, 'html.parser')

should I do this

    def __init__(self, html_data=None):
        try:
            self.bs = BeautifulSoup(html_data, 'html.parser')
        except:
            pass

both works but I am a bit confused of how to use one over the other and when to use them.

what should happen if `html_data` is `None`? Is `self.bs` initialized to something else? — Dimitris Fasarakis Hilliard, Sep 30 '17 at 11:25
Related: [Python Forgiveness vs. Permission and Duck Typing](//softwareengineering.stackexchange.com/q/175655) — Martijn Pieters, Sep 30 '17 at 11:27
if html_data is None, BeafutifulSoup will raise an error. I was making the class more flexible by letting you pass the html_data while initializing the class. — , Sep 30 '17 at 11:30
Thanks @MartijnPieters, I should learn how to find these answers on stackoverflow. — , Sep 30 '17 at 11:32
Point was that if `html_data` is `None` and no viable alternative exists you bail out i.e let the exception bubble up or catch the exception and raise a more appropriate one. — Dimitris Fasarakis Hilliard, Sep 30 '17 at 11:45

When to use if-else statement or try-except statements during exception handling?

0 Answers0