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c# barcode generator library And Finally . . . in Font
And Finally . . . PDF 417 Drawer In None Using Barcode printer for Font Control to generate, create PDF417 image in Font applications. www.OnBarcode.comPainting EAN128 In None Using Barcode generation for Font Control to generate, create GS1-128 image in Font applications. www.OnBarcode.comFinally, there is the finally clause. You use it to do housekeeping after a possible exception. It is combined with a try clause: x = None try: x = 1/0 Create Data Matrix 2d Barcode In None Using Barcode creator for Font Control to generate, create ECC200 image in Font applications. www.OnBarcode.comCreating UPC Symbol In None Using Barcode encoder for Font Control to generate, create Universal Product Code version A image in Font applications. www.OnBarcode.comCHAPTER 8 EXCEPTIONS
Create Code 128 Code Set B In None Using Barcode generator for Font Control to generate, create Code 128C image in Font applications. www.OnBarcode.comPainting Barcode In None Using Barcode generator for Font Control to generate, create Barcode image in Font applications. www.OnBarcode.comfinally: print 'Cleaning up...' del x In the preceding example, you are guaranteed that the finally clause will be executed, no matter what exceptions occur in the try clause. The reason for initializing x before the try clause is that otherwise it would never be assigned a value because of the ZeroDivisionError. This would lead to an exception when using del on it within the finally clause, which you wouldn t catch. If you run this, the cleanup comes before the program crashes and burns: Cleaning up... Traceback (most recent call last): File "C:\python\div.py", line 4, in x = 1/0 ZeroDivisionError: integer division or modulo by zero While using del to remove a variable is a rather silly kind of cleanup, the finally clause may be quite useful for closing files or network sockets and the like. (More on those in 14.) You can also combine try, except, finally, and else (or just three of them) in a single statement: try: 1/0 except NameError: print "Unknown variable" else: print "That went well!" finally: print "Cleaning up." Painting PDF417 In None Using Barcode printer for Font Control to generate, create PDF 417 image in Font applications. www.OnBarcode.comUniform Symbology Specification Code 93 Maker In None Using Barcode printer for Font Control to generate, create Uniform Symbology Specification Code 93 image in Font applications. www.OnBarcode.com Note In Python versions prior to 2.5, the finally clause had to be used on its own it couldn t be used Creating PDF-417 2d Barcode In None Using Barcode creator for Online Control to generate, create PDF417 image in Online applications. www.OnBarcode.comPDF417 Generator In Visual Studio .NET Using Barcode creator for Visual Studio .NET Control to generate, create PDF 417 image in VS .NET applications. www.OnBarcode.comin the same try statement as an except clause. If you wanted both, you needed to wrap two statements. From Python 2.5 onwards, you can combine these to your heart s content, though. Generate Code-39 In Java Using Barcode creator for BIRT Control to generate, create Code 3 of 9 image in BIRT applications. www.OnBarcode.comQR Code Scanner In .NET Using Barcode scanner for VS .NET Control to read, scan read, scan image in VS .NET applications. www.OnBarcode.comExceptions and Functions
Recognize Barcode In VB.NET Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET applications. www.OnBarcode.comCreate UCC.EAN - 128 In Visual Studio .NET Using Barcode encoder for Reporting Service Control to generate, create GS1-128 image in Reporting Service applications. www.OnBarcode.comExceptions and functions work together quite naturally. If an exception is raised inside a function, and isn t handled there, it propagates (bubbles up) to the place where the function was called. If it isn t handled there either, it continues propagating until it reaches the main program (the global scope), and if there is no exception handler there, the program halts with a stack trace. Let s take a look at an example: >>> def faulty(): ... raise Exception('Something is wrong') ... Barcode Generation In Java Using Barcode creator for Java Control to generate, create Barcode image in Java applications. www.OnBarcode.comPrint Barcode In .NET Using Barcode creator for .NET framework Control to generate, create Barcode image in VS .NET applications. www.OnBarcode.comCHAPTER 8 EXCEPTIONS
ANSI/AIM Code 39 Decoder In Visual Basic .NET Using Barcode recognizer for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications. www.OnBarcode.comGenerate UCC - 12 In None Using Barcode maker for Software Control to generate, create GTIN - 128 image in Software applications. www.OnBarcode.com>>> def ignore_exception(): ... faulty() ... >>> def handle_exception(): ... try: ... faulty() ... except: ... print 'Exception handled' ... >>> ignore_exception() Traceback (most recent call last): File '<stdin>', line 1, in File '<stdin>', line 2, in ignore_exception File '<stdin>', line 2, in faulty Exception: Something is wrong >>> handle_exception() Exception handled As you can see, the exception raised in faulty propagates through faulty and ignore_exception, and finally causes a stack trace. Similarly, it propagates through to handle_exception, but there it is handled with a try/except statement. Universal Product Code Version A Creator In None Using Barcode drawer for Online Control to generate, create UPC Code image in Online applications. www.OnBarcode.comPainting Code 128C In Java Using Barcode generator for BIRT reports Control to generate, create Code-128 image in Eclipse BIRT applications. www.OnBarcode.comThe Zen of Exceptions
Exception handling isn t very complicated. If you know that some part of your code may cause a certain kind of exception, and you don t simply want your program to terminate with a stack trace if and when that happens, then you add the necessary try/except or try/finally statements (or some combination thereof) to deal with it, as needed. Sometimes, you can accomplish the same thing with conditional statements as you can with exception handling, but the conditional statements will probably end up being less natural and less readable. On the other hand, some things that might seem like natural applications of if/else may in fact be implemented much better with try/except. Let s take a look at a couple of examples. Let s say you have a dictionary and you want to print the value stored under a specific key, if it is there. If it isn t there, you don t want to do anything. The code might be something like this: def describePerson(person): print 'Description of', person['name'] print 'Age:', person['age'] if 'occupation' in person: print 'Occupation:', person['occupation']
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