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Python Built In Error Types


Exceptions are known to non-programmers as instances that do not conform to a general rule. When you create custom Exception classes for your application, many of them do not subclass just from Exception, but from others, like ValueError or similar. That's not a whole lot of extra code you need per class. ;) share|improve this answer answered Aug 23 '09 at 21:58 Lennart Regebro 75k17134202 add a comment| Your Answer Enjoy! ##What is an Exception? check over here

except: ... import os for i in range(10): print i, os.ttyname(i) $ python exceptions_OSError.py 0 /dev/ttys000 1 Traceback (most recent call last): File "exceptions_OSError.py", line 15, in print i, os.ttyname(i) OSError: [Errno For example, when trying to reference an attribute that does not exist: class NoAttributes(object): pass o = NoAttributes() print o.attribute $ python exceptions_AttributeError.py Traceback (most recent call last): File "exceptions_AttributeError.py", line I strive to find analogies that can be understood without any other knowledge of programming. https://docs.python.org/2/library/exceptions.html

Python Custom Exception

Concrete exceptions 5.2.1. f = open('/does/not/exist', 'r') $ python exceptions_IOError.py Traceback (most recent call last): File "exceptions_IOError.py", line 12, in f = open('/does/not/exist', 'r') IOError: [Errno 2] No such file or directory: '/does/not/exist' An implicitly chained exception in __context__ is shown only if __cause__ is None and __suppress_context__ is false. Traceback (most recent call last): File "finally.py", line 3, in x = float(raw_input("Your number: ")) ValueError: invalid literal for float(): Python [email protected]:~/tmp$ Combining try, except and finally "finally" and "except"

Here’s a little summary: Not all exceptions are created equal: if you know what class of exception you are dealing with, then be specific about what you catch Don’t catch anything And because if the deprecation, you then need both, or you get an error. try: ... Python Exception Class Methods That was no valid number.

exception TabError¶ Raised when indentation contains an inconsistent use of tabs and spaces. Some built-in exceptions (like IOError) expect a certain number of arguments and assign a special meaning to the elements of this tuple, while others are usually called only with a import unittest class AssertionExample(unittest.TestCase): def test(self): self.failUnless(False) unittest.main() $ python exceptions_AssertionError_unittest.py F ====================================================================== FAIL: test (__main__.AssertionExample) ---------------------------------------------------------------------- Traceback (most recent call last): File "exceptions_AssertionError_unittest.py", line 17, in test self.failUnless(False) AssertionError: False https://docs.python.org/3/tutorial/errors.html def __init__(self, message): ...

An explicitly chained exception in __cause__ is always shown when present. Python Errno It is a subclass of ValueError. UnicodeError has attributes that describe the encoding or decoding error. exception AssertionError¶ Raised when an assert statement fails. So Python complains again by raising an IndexError and printing an appropriate traceback.

Python Valueerror Example

The exception inherits from BaseException so as to not be accidentally caught by code that catches Exception and thus prevent the interpreter from exiting. Bonuses print "dealing with IndexError" ... Python Custom Exception assert i >= 1 ... Python Exception Message Corresponds to errno ESRCH.

Whenever these type of runtime error occur, Python creates an exception object. http://caribtechsxm.com/python-exception/python-try-except-error-types.php exception OSError([arg])¶ exception OSError(errno, strerror[, filename[, winerror[, filename2]]]) This exception is raised when a system function returns a system-related error, including I/O failures such as "file not found" or "disk full" Many programming languages like C++, Objective-C, PHP, Java, Ruby, Python, and many others have built-in support for exception handling. If you are having any trouble understanding how the program flow can be determined from a traceback message, then it will likely be worth your while to do some reading about Python Filenotfounderror

  1. The interpreter does not raise this exception itself very often, but some user code does.
  2. Goodbye, world!
  3. Naturally this also isn’t cool.

exception SyntaxError¶ Raised when the parser encounters a syntax error. In either case, the exception itself is always shown after any chained exceptions so that the final line of the traceback always shows the last exception that was raised. 5.1. exception TypeError¶ Raised when an operation or function is applied to an object of inappropriate type. this content except: ...

Long integers allocate more space as values grow, so they end up raising MemoryError. Python Attributeerror Object Has No Attribute Be sure to report the version of the Python interpreter (sys.version; it is also printed at the start of an interactive Python session), the exact error message (the exception's associated exception AttributeError¶ Raised when an attribute reference (see Attribute references) or assignment fails. (When an object does not support attribute references or attribute assignments at all, TypeError is raised.) exception

Will change it tomorrow –Alvaro Feb 4 '15 at 1:54 1 good critique!

exception UnicodeError¶ Raised when a Unicode-related encoding or decoding error occurs. The associated value is a string giving details about the type mismatch. Conversely, if you have an except block aimed at MyIndexErrors, then it will NOT catch IndexErrors. Assertionerror Python Some of the common built-in exceptions in Python programming along with the error that cause then are tabulated below.

exception KeyboardInterrupt¶ Raised when the user hits the interrupt key (normally Control-C or Delete). It is a subclass of UnicodeError. I'll demonstrate both errors: >>> ValidationError('foo', 'bar', 'baz').message Traceback (most recent call last): File "", line 1, in ValidationError('foo', 'bar', 'baz').message TypeError: __init__() takes exactly 3 arguments (4 given) >>> have a peek at these guys SyntaxError Raised by parser when syntax error is encountered.

During execution, a check for interrupts is made regularly.