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Python Return Error String


The answer may surprise you: the list raises a StopIteration exception. A "pre-processed" stack trace entry is a 4-tuple (filename, line number, function name*, text) representing the information that is usually printed for a stack trace. It should be noted that just using str will return an empty string if there's no error message whereas using repr as pyfunc recommends will at least display the class of except (RuntimeError, TypeError, NameError): ... this content

Their names are PyExc_Warning, PyExc_UserWarning, PyExc_UnicodeWarning, PyExc_DeprecationWarning, PyExc_SyntaxWarning, PyExc_RuntimeWarning, and PyExc_FutureWarning. PyExc_Warning is a subclass of PyExc_Exception; the other warning categories are If not, AddError will have no effect. arcpy.AddError(e.args[0]) The try statement has an optional finally clause that can be used for That was no valid number. finally: ... http://stackoverflow.com/questions/16451514/returning-error-string-from-a-function-in-python

Python Get Exception Message

Errors and Exceptions¶ Until now error messages haven't been more than mentioned, but if you have tried out the examples you have probably seen some. In fact, I guarantee your code is already using exceptions, even if not explicitly. Classes This Page Report a Bug Show Source Navigation index modules | next | previous | Python » 3.5.2 Documentation » The Python Tutorial » | © Copyright 2001-2016, Python Software traceback.extract_stack([f[, limit]])¶ Extract the raw traceback from the current stack frame.

  1. A raise statement can be used for this purpose.
  2. It isn't such a problem with python code, because the language is supposed to take care of fixing accounting-type invariants for you. -jJ) This is a better argument for *careful* use
  3. Exception classes can be defined which do anything any other class can do, but are usually kept simple, often only offering a number of attributes that allow information about the error
  4. int PyUnicodeDecodeError_GetStart(PyObject*exc, Py_ssize_t*start)¶ int PyUnicodeEncodeError_GetStart(PyObject*exc, Py_ssize_t*start)¶ int PyUnicodeTranslateError_GetStart(PyObject*exc, Py_ssize_t*start)¶ Get the start attribute of the given exception object and place it into *start.
  5. def calculate_value(self, foo, bar, baz): try: result = self._do_calculation(foo, bar, baz) except: self.user_screwups += 1 raise return result Here, we have a member function doing some calculation.
  6. If the error indicator is not set, set all three variables to NULL.
  7. void PyErr_PrintEx(intset_sys_last_vars)¶ Print a standard traceback to sys.stderr and clear the error indicator.
  8. When an exception occurs, it may have an associated value, also known as the exception's argument.
  9. Changing the chance of an exception to 20% gives the following result: using if statement: minimum: 1.49791312218 per_lookup: 1.49791312218e-06 using exception: minimum: 1.92286801338 per_lookup: 1.92286801338e-06 At this point the numbers are
  10. Same idea, much easier to follow (the lines in the try block could obviously be combined but weren't to make the example more clear).

For convenience, the exception instance defines __str__() so the arguments can be printed directly without having to reference .args. PyObject* PyErr_NewException(char*name, PyObject*base, PyObject*dict)¶ Return value: New reference.This utility function creates and returns a new exception class. Where can I find my minimum tire pressure? Python Print Exception The arguments are the exception type, etype and value such as given by sys.last_type and sys.last_value.

If possible, the repr of obj will be printed in the warning message. So an exception that does nothing is cheap. PyObject* PyUnicodeDecodeError_Create(const char*encoding, const char*object, Py_ssize_tlength, Py_ssize_tstart, Py_ssize_tend, const char*reason)¶ Create a UnicodeDecodeError object with the attributes encoding, object, length, start, end and reason. Normally, raise is paired with an exception to be raised.

print str(e) ... Python Custom Exception Another use of else is when code in the try block requires some cleanup (and doesn't have a usable context manager), as in the below example: def display_username(user_id): try: db_connection = Otherwise, zero is returned. x = int(raw_input("Please enter a number: ")) ...

Python Exception Class

NameError("name 'x' is not defined",) >>> Using str: >>> >>> try: ... python python-2.7 python-3.x share|improve this question asked May 8 '13 at 22:48 KT100 4261925 2 Why not exceptions? –Waleed Khan May 8 '13 at 22:50 add a comment| 2 Answers Python Get Exception Message Defining Clean-up Actions 8.7. Python Exception Stack Trace x = int(input("Please enter a number: ")) ...

You *can* do it, say, with recursive generators, but it is difficult.) Joel's concern about multiple exit points is good advice, but it can be taken too far. news raise ... void PyErr_Print()¶ Alias for PyErr_PrintEx(1). This way you can modify the arguments and re-raise, and the extra information will be displayed. Syntax For Generic Except Clause In Python

int PyErr_GivenExceptionMatches(PyObject*given, PyObject*exc)¶ Return true if the given exception matches the exception in exc. For example: >>> raise NameError('HiThere') Traceback (most recent call last): File "", line 1, in NameError: HiThere The sole argument to raise indicates the exception to be raised. The TypeError raised by dividing two strings is not handled by the except clause and therefore re-raised after the finally clause has been executed. have a peek at these guys A simple example to demonstrate the finally clause: try: x = float(input("Your number: ")) inverse = 1.0 / x finally: print("There may or may not have been an exception.") print("The inverse:

x = 1/0 ... >>> try: ... Python Try Without Except more hot questions question feed lang-py about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Last updated on Sep 20, 2016.

They are needed if the recursive code does not necessarily invoke Python code (which tracks its recursion depth automatically).

HandlingExceptions (last edited 2015-11-06 01:04:13 by ElephantJim) MoinMoin PoweredPython PoweredGPL licensedValid HTML 4.01 Unable to edit the page? String exceptions are one example of an exception that doesn't inherit from Exception. -- MikeRovner I believe that as of 2.7, exceptions still don't have to be inherited from Exception or The previous example is nearly the same as: import sys file_name = sys.argv[1] text = [] try: fh = open(file_name, 'r') except IOError: print('cannot open', file_name) else: text = fh.readlines() fh.close() Python Try Except Else except Exception, e: ...

We show this in the following interactive session: >>> n = int(input("Please enter a number: ")) Please enter a number: 23.5 Traceback (most recent call last): File "", line 1, in Quote of the Day:"The difference between stupidity and genius is that genius has its limits" (Albert Einstein)

Previous Chapter: Iterators and Generators Next Chapter: Tests, DocTests, UnitTests Errors and Exceptions Python allows you to write a routine that automatically runs when a system error is generated. http://caribtechsxm.com/python-exception/python-exception-string-error.php Call this function only when the error indicator is set. (Otherwise it will cause a fatal error!) If set_sys_last_vars is nonzero, the variables sys.last_type, sys.last_value and sys.last_traceback will

try: ... But is there a better, more interesting way to get at that information that people know of? This whole section is a bit weak, maybe it would be better to just state "don't overuse exceptions as that can lead to hard-to-verify spaghetti code" and be done with it Browse other questions tagged python python-2.7 python-3.x or ask your own question.

PyObject* PyUnicodeTranslateError_Create(const Py_UNICODE*object, Py_ssize_tlength, Py_ssize_tstart, Py_ssize_tend, const char*reason)¶ Create a UnicodeTranslateError object with the attributes object, length, start, end and reason. But it doesn't hold true for Python. (The difference is that Python reduces the chances of an error in the first place, and makes raising an exception the clean way to print type(inst) # the exception instance ... If you've avoided exceptions like the plague, it's time to give them another look.

a Python/C API function) was invoked with an illegal argument. int PyUnicodeDecodeError_SetEnd(PyObject*exc, Py_ssize_tend)¶ int PyUnicodeEncodeError_SetEnd(PyObject*exc, Py_ssize_tend)¶ int PyUnicodeTranslateError_SetEnd(PyObject*exc, Py_ssize_tend)¶ Set the end attribute of the given exception object to end. int Py_EnterRecursiveCall(const char*where)¶ Marks a point where a recursive C-level call is about to be performed. That will most certainly lead to unmaintainable and difficult to understand code.

Input and Output Next topic 9. Sessions can be held remotely using Google+/Skype or in-person if you're in the NYC area. raise KeyboardInterrupt ... Handling run-time error: division by zero 8.4.

except NameError: ... But at most one except clause will be executed. The optional f argument can be used to specify an alternate stack frame to start. Last updated on Sep 30, 2016.

File name and line number are printed so you know where to look in case the input came from a script. 8.2. One may also instantiate an exception first before raising it and add any attributes to it as desired. >>> try: ... Use traceback.print_exc() to print the current exception to standard error, just like it would be printed if it remained uncaught, or traceback.format_exc() to get the same output as a string. The following sections offer a few techniques that introduce the basics of Python exception handling.When a tool writes an error message, ArcPy generates an arcpy.ExecuteError exception.