Python Error Handling Keyerror
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Python Exceptions List
Stack Overflow the company Business Learn more about hiring developers or posting ads with python custom exception us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is python filenotfounderror a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Catch KeyError in Python up vote 9 down vote favorite 3 If I run
Python Exception Message
the code: connection = manager.connect("I2Cx") The program crashes and reports a KeyError because I2Cx doesn't exist (it should be I2C). But if I do: try: connection = manager.connect("I2Cx") except Exception, e: print e It doesn't print anything for e. I would like to be able to print the exception that was thrown. If I try the same thing with a divide by zero operation it is caught and reported properly
Python Valueerror Example
in both cases. What am I missing here? python try-catch except share|improve this question edited Apr 22 '13 at 18:36 asked Apr 22 '13 at 18:23 spizzak 2471512 4 Side note: Unless you need pre-2.5 compatibility, you should write except Exception as e: instead of except Exception, e:. –abarnert Apr 22 '13 at 18:47 add a comment| 4 Answers 4 active oldest votes up vote 18 down vote If it's raising a KeyError with no message, then it won't print anything. If you do... try: connection = manager.connect("I2Cx") except Exception, e: print repr(e) ...you'll at least get the exception class name. A better alternative is to use multiple except blocks, and only 'catch' the exceptions you intend to handle... try: connection = manager.connect("I2Cx") except KeyError, e: print 'I got a KeyError - reason "%s"' % str(e) except IndexError, e: print 'I got an IndexError - reason "%s"' % str(e) There are valid reasons to catch all exceptions, but you should almost always re-raise them if you do... try: connection = manager.connect("I2Cx") except KeyError, e: print 'I got a KeyError - reason "%s"' % str(e) except: print 'I got another exception, but I should re-raise' raise ...because you probably don't want to handle KeyboardInterrupt if the user pres
This module never needs to be imported explicitly: the exceptions are provided in the built-in namespace as well as the exceptions module. For class exceptions, in a try statement with an except clause that mentions a particular class,
Python Errno
that clause also handles any exception classes derived from that class (but not exception classes from which it is python attributeerror object has no attribute derived). Two exception classes that are not related via subclassing are never equivalent, even if they have the same name. The built-in exceptions listed below can be generated by the interpreter http://stackoverflow.com/questions/16154032/catch-keyerror-in-python or built-in functions. Except where mentioned, they have an "associated value" indicating the detailed cause of the error. This may be a string or a tuple containing several items of information (e.g., an error code and a string explaining the code). The associated value is the second argument to the raise statement. If the exception class is derived from the standard root https://docs.python.org/2/library/exceptions.html class BaseException, the associated value is present as the exception instance's args attribute. User code can raise built-in exceptions. This can be used to test an exception handler or to report an error condition "just like" the situation in which the interpreter raises the same exception; but beware that there is nothing to prevent user code from raising an inappropriate error. The built-in exception classes can be subclassed to define new exceptions; programmers are encouraged to derive new exceptions from the Exception class or one of its subclasses, and not from BaseException. More information on defining exceptions is available in the Python Tutorial under User-defined Exceptions. The following exceptions are only used as base classes for other exceptions. exception BaseException¶ The base class for all built-in exceptions. It is not meant to be directly inherited by user-defined classes (for that, use Exception). If str() or unicode() is called on an instance of this class, the representation of the argument(s) to the instance are returned, or the empty string when there were no arguments. New in version 2.5. args¶ T
a try statement with an except clause that mentions a particular class, that clause also handles any exception https://docs.python.org/3/library/exceptions.html classes derived from that class (but not exception classes from which it http://www.java2s.com/Tutorial/Python/0060__Statement/CatchKeyErrorandAssertionError.htm is derived). Two exception classes that are not related via subclassing are never equivalent, even if they have the same name. The built-in exceptions listed below can be generated by the interpreter or built-in functions. Except where mentioned, they have an "associated value" indicating the python exception detailed cause of the error. This may be a string or a tuple of several items of information (e.g., an error code and a string explaining the code). The associated value is usually passed as arguments to the exception class's constructor. User code can raise built-in exceptions. This can be used to test an exception handler or to python error handling report an error condition "just like" the situation in which the interpreter raises the same exception; but beware that there is nothing to prevent user code from raising an inappropriate error. The built-in exception classes can be subclassed to define new exceptions; programmers are encouraged to derive new exceptions from the Exception class or one of its subclasses, and not from BaseException. More information on defining exceptions is available in the Python Tutorial under User-defined Exceptions. When raising (or re-raising) an exception in an except or finally clause __context__ is automatically set to the last exception caught; if the new exception is not handled the traceback that is eventually displayed will include the originating exception(s) and the final exception. When raising a new exception (rather than using a bare raise to re-raise the exception currently being handled), the implicit exception context can be supplemented with an explicit cause by using from with raise: raise new_exc from original_exc The expression following fr
: except«Statement«Python TutorialPython TutorialStatementexceptimport sys, string matrix = {"brazil":"br","france":"fr","argentina":"ar","usa":"us"} def getcode(country): try: data = matrix[string.lower(country)] assert data != "br", "You cannot select this country for this action!" return data except KeyError: print sys.exc_type, ":", "%s is not in the list." % sys.exc_value print except AssertionError, b: print b print while 1: country = raw_input("Enter the country name or press x to exit: ") if country == "x": break code = getcode(country) if code != None: print "%s's country code is %s" % (country, code) print 3.10.except3.10.1.Catching Two Exceptions3.10.2.Simple exception handling example.3.10.3.Demonstrating exception arguments and stack unwinding.3.10.4.Catch more than on exceptions3.10.5.Catch KeyError and AssertionError3.10.6.try/except block that checks for correct user input3.10.7.try/except block with string argumentjava2s.com |Email:info at java2s.com|© Demo Source and Support. All rights reserved.