raise in raise error

Question

I have an error raise eb : list index out of range.

I don't understand why when i do a raise in an other try - catch I'm doing a try - catch in a try - catch and both raises errors.

Here is my code and the error line is at raise eb :

try:
    print("debut edit")
    print(p)
    modif_box = get_modif_box_profile(p)
    post_box = get_Post_Box(p)
    print("modi_box")
    print(modif_box)
    print("mbu id")
    print(modif_box.id)
    diff = {}
    posts = {}
    new_post = []
    diff["posts"] = posts
    posts["modified_post"] = new_post
    for post in modif_box.edit_post_user.all():
        # print(post.id_mod)
        try:
            messagenew = post_box.post.all().filter(id=post.id_mod)[0]
            # print(post_new)
            print("posts")
            print(post)
            # todo a factoriser
            if messagenew.id > int(last_id) and messagenew.sender.id != p.id:
                name = get_name_contact(p, messagenew)
                return_post = {}
                return_post["uid"] = messagenew.sender.id
                return_post["pid"] = messagenew.id
                return_post["author"] = name
                return_post["title"] = messagenew.title
                return_post["date"] = unix_time_millis(messagenew.date)
                return_post["smile"] = count_smile(messagenew)
                return_post["comment"] = count_comment(messagenew)
                return_post["data"] = messagenew.data
                return_post["type"] = messagenew.type_post.type_name
                new_post.append(return_post)
            else:
                print("depop edit")
                modif_box.edit_post_user.remove(post)
                modif_box.save()
        except Exception as eb:
            PrintException()
            # raise eb (if i decomment here i have an error in my program)
    print(diff)
    return diff
except Exception as e:
    PrintException()
    raise e

Regards and thanks

Answer 1

If you comment the raise statement there, it doesn't mean that you don't have an Error; it simply means that you handled the Exception -- which in your case is from what I can tell an IndexError -- by catching it with the except Exception and then calling PrintException().

When you raise an exception what you actually do is:

The raise statement allows the programmer to force a specified exception to occur.

So, by un-commenting, you allow the IndexError named eb to re-appear after catching it in the inner try-except block and get caught by the outer try - except clause in which you again re-raise it.

---

Generally, you don't want to catch exceptions in such a generic way because it might hide some unpredicted behaviour of the program that you would like to know about.

Limit the exceptions you catch in the except clause by simply specifying them, in your case, an except clause of the form:

except IndexError as eb:
    PrintException() 

would probably suffice.