Raise two errors at the same time

Question

Is there any way to raise two errors at the same time by using try and except? For example, ValueError and KeyError.

How do I do that?

Answer 1

You can Raise more than one exception like this:

try:
    i = 0
    j = 1 / i
except ZeroDivisionError:
    try:
        i = 'j'
        j = 4 + i
    except TypeError:
        raise ValueError

NOTE: it may be that only the ValueError is raised but this error message seems right:

Traceback (most recent call last):
  File "<pyshell#9>", line 3, in <module>
    j = 1 / i
ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<pyshell#9>", line 7, in <module>
    j = 4 + i
TypeError: unsupported operand type(s) for +: 'int' and 'str'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<pyshell#9>", line 9, in <module>
    raise ValueError
ValueError

Answer 2

You could raise an error which inherits from both ValueError and KeyError. It would get caught by a catch block for either.

class MyError(ValueError, KeyError):
    ...

Answer 3

Yes, you can handle more than one error, either using

try:
    # your code here
except (ValueError, KeyError) as e:
    # catch it, the exception is accessable via the variable e

Or, directly add two "ways" of handling different errors:

try:
    # your code here
except ValueError as e:
    # catch it, the exception is accessable via the variable e
except KeyError as e:
    # catch it, the exception is accessable via the variable e

You may also leave out the "e" variable.

Checkout the documentation: http://docs.python.org/tutorial/errors.html#handling-exceptions

Answer 4

The solution from @shrewmouse still requires to choose an exception class to wrap the caught exceptions.

• Following solution uses Exception Chaining via finally to execute code after one exception occurs
• We don't need to know beforehand, what exceptions occur
• Note that only the first exception that occurs can be detected from the caller via except
  • if this is a problem, use @Collin's solution above to inherit from all collected exceptions
• You'll see the exceptions separated by:
  "During handling of the above exception, another exception occurred:"

def raise_multiple(errors):
    if not errors:  # list emptied, recursion ends
        return
    try:
        raise errors.pop()  # pop removes list entries
    finally:
        raise_multiple(errors)  # recursion

---

If you have a task that needs to be done for each element of a list, you don't need to collect the Exceptions beforehand. Here's an example for multiple file deletion with multiple error reporting:

def delete_multiple(files):
    if not files:
        return
    try:
        os.remove(files.pop())
    finally:
        delete_multiple(files)

---

PS:
Tested with Python 3.8.5
To print full traceback per exception have a look at traceback.print_exc
The original question is answered since years. But as this page is the top search result for "python raise multiple" I share my approach to fill an (IMHO relevant) gap in the solution spectrum.

Answer 5

The question asks how to RAISE multiple errors not catch multiple errors.

Strictly speaking you can't raise multiple exceptions but you could raise an object that contains multiple exceptions.

raise Exception(
    [
        Exception("bad"),
        Exception("really bad"),
        Exception("really really bad"),
    ]
)

Question: Why would you ever want to do this?
Answer: In a loop when you want to raise an error but process the loop to completion.

For example when unit-testing with unittest2 you might want to raise an exception and keep processing then raise all of the errors at the end. This way you can see all of the errors at once.

def test_me(self):

    errors = []

    for modulation in self.modulations:
        logging.info('Testing modulation = {modulation}'.format(**locals()))

        self.digitalModulation().set('value', modulation)
        reply = self.getReply()

        try: 
            self._test_nodeValue(reply, self.digitalModulation())
        except Exception as e:
            errors.append(e)

    if errors:
        raise Exception(errors)

Answer 6

try :
    pass
except (ValueError,KeyError):
    pass

read more about Handling exceptions