How do I use raise correctly?

Question

Can someone please help me to get some kind of structure in this code? I am new to this. The errors should capture both non-existing files, and files that do not contain rows of four parts separated by ";".

The program should look something like this:

Name of quiz-file: hejsan
"That resulted in an input/output error, please try again!"

Name of quiz-file: namn.csv
"The file is not on the proper format. There needs to be four strings, separated by ; in each line of the file."

Name of quiz-file: quiz.csv

Where quiz.csv fullfills all the requirements!

def get_quiz_list_handle_exceptions():
    success = True
    while success:
        try:

            file = input("Name of quiz-file: ")
            file2 = open(file,'r')

            for lines in range(0,9):
                quiz_line = file2.readline()
                quiz_line.split(";")

                if len(quiz_line) != 4:
                    raise Exception

    except FileNotFoundError as error:
        print("That resulted in an input/output error, please try again!", error)

    except Exception:
        print("The file is not on the proper format. There needs to be four strings, separated by ; in each line of the file.")

    else:
    success = False


get_quiz_list_handle_exceptions()

The answers to the question [Asking the user for input until they give a valid response](https://stackoverflow.com/questions/23294658/asking-the-user-for-input-until-they-give-a-valid-response) may help. — martineau, Feb 13 '19 at 22:20
Your `except` clauses indentation is wrong. Align them with the `try`. The same for the statement after the `else`. Add four spaces. — progmatico, Feb 13 '19 at 22:20

score 0 · Answer 1 · answered Feb 13 '19 at 22:49

There is an indentation mistake in your code

def get_quiz_list_handle_exceptions():
success = True
while success:
    try:

        file = input("Name of quiz-file: ")
        file2 = open(file,'r')

        for lines in range(0,9):
            quiz_line = file2.readline()
            quiz_line.split(";")

            if len(quiz_line) != 4:
                raise Exception

    except FileNotFoundError as error:
        print("That resulted in an input/output error, please try again!", error)

    except Exception:
        print("The file is not on the proper format. There needs to be four strings, separated by ; in each line of the file.")
    else:
        success = False


get_quiz_list_handle_exceptions()

score 0 · Accepted Answer · answered Feb 13 '19 at 22:57

You have numerous issues:

Failure to indent properly in several locations
Failure to keep the results of split, so your length test is testing a string's length, not the number of semi-colon separated components
(Minor) Not using with statements, nor closing your file, so the file handle could conceivably be left open indefinitely (depends on Python interpreter)

Fixed code:

def get_quiz_list_handle_exceptions():
    success = True
    while success:
        try:

            file = input("Name of quiz-file: ")
            with open(file,'r') as file2:  # Use with statement to guarantee file is closed
                for lines in range(0,9):
                    quiz_line = file2.readline()
                    quiz_line = quiz_line.split(";")

                    if len(quiz_line) != 4:
                        raise Exception

        # All your excepts/elses were insufficiently indented to match the try
        except FileNotFoundError as error:
            print("That resulted in an input/output error, please try again!", error)

        except Exception:
            print("The file is not on the proper format. There needs to be four strings, separated by ; in each line of the file.")
        else:
            success = False  # Fixed indent


get_quiz_list_handle_exceptions()

How do I use raise correctly?

2 Answers2