{"id":923,"date":"2024-09-17T10:16:58","date_gmt":"2024-09-17T10:16:58","guid":{"rendered":"https:\/\/www.zframez.com\/articles\/?p=923"},"modified":"2024-10-16T16:02:58","modified_gmt":"2024-10-16T16:02:58","slug":"chapter-12-exception-handling-in-python-techniques-and-examples","status":"publish","type":"post","link":"https:\/\/www.zframez.com\/articles\/python-tutorials\/chapter-12-exception-handling-in-python-techniques-and-examples","title":{"rendered":"Chapter 12: Exception Handling in Python -Techniques and Examples"},"content":{"rendered":"\n
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Understanding Exception Handling in Python<\/strong><\/h1>\n\n\n\n

What is an Exception?<\/strong><\/p>\n\n\n\n

Exceptions are errors that occur during the execution of your code. Before running a script, Python checks for syntax errors, but even if the syntax is correct, runtime errors, called exceptions, can still occur. In this chapter, we\u2019ll explore how exceptions work in Python and how you can handle them using try<\/code>, except<\/code>, else<\/code>, and finally<\/code><\/strong> blocks. We\u2019ll also cover handling multiple exceptions, raising your own exceptions, and using the assert<\/code> statement for validation. By the end of this chapter, you\u2019ll know how to handle errors gracefully in your programs and ensure they run smoothly even when something goes wrong.<\/p>\n\n\n\n

For example, in the code below, there are no syntax errors. However, during execution, the 2nd line \u201cc = a \/ <\/code>b<\/strong>\u201d will cause an exception because the value of the variable \u201cb\u201d is zero and dividing by zero is not allowed.<\/p>\n\n\n\n

a, b = 10, 0\nc = a \/ b\n\n#Output:\nTraceback (most recent call last):\n  File \"except.py\", line 2, in <module>\n    c = a \/ b\nZeroDivisionError:<\/strong> division by zero<\/code><\/pre>\n\n\n\n
Some other common exceptions are: ValueError, TypeError, NameError, SyntaxError, FileNotFound Error<\/strong> etc<\/p>\n\n\n\n
ValueError :<\/strong> This exception is raised when a function gets a valid data type but an invalid value. For example, trying to convert a non-numeric string into an integer as show in below code:<\/p>\n\n\n\n
a = \"hi\"\nb = int(a)\n\n#Output:\nTraceback (most recent call last):\n  File \"except.py\", line 2, in <module>\n    b = int(a)\nValueError: invalid literal for int() with base 10: 'hi'<\/code><\/pre>\n\n\n\n
TypeError<\/strong>: Raised when you perform an operation on a data type that doesn\u2019t support it. For example, trying to add a string and an integer together as shown below:<\/p>\n\n\n\n
a = \"hello\" + 5\n\n#Output :\nTraceback (most recent call last):\n  File \"except.py\", line 1, in <module>\n    a = \"hello\" + 5\nTypeError: can only concatenate str (not \"int\") to str<\/code><\/pre>\n\n\n\n
NameError<\/strong>: Raised when a variable or function name is not found in the local or global namespace. For example, the following simple code uses a variable that hasn\u2019t been defined and will raise a NameError.<\/p>\n\n\n\n
a = hello\n\n#Output: \nTraceback (most recent call last):\n  File \"except.py\", line 1, in <module>\n    a = hello\nNameError: name 'hello' is not defined<\/code><\/pre>\n\n\n\n
 FileNotFoundError:<\/strong> Raised when attempting to open a file that does not exist. For example, the following code uses the open<\/code> function to open the file abcd.txt<\/code> in read-only mode and will raise a FileNotFoundError if the file does not exist in the same folder as the script.<\/p>\n\n\n\n
file_id = open (\"abcd.txt\" , r) \n\n#Output:\nTraceback (most recent call last):\n  File \"except.py\", line 1, in <module>\n    fid = open(\"abcd.txt\", 'r')\nFileNotFoundError: [Errno 2] No such file or directory: 'abcd.txt'<\/code><\/pre>\n\n\n\n
What is Exception Handling?<\/strong><\/h2>\n\n\n\n
Exception handling is the technique of catching errors to prevent the unexpected termination of a script. If you suspect a part of your code may raise an error, you can use the try-except<\/strong> block to handle that exception.<\/p>\n\n\n\n
For example, to handle the FileNotFoundError<\/code> in the code above:<\/p>\n\n\n\n
try:\n    fid = open(\"abcd.txt\", 'r')\nexcept FileNotFoundError:\n    print(\"File is not present, skipping the reading process...\")\nelse:\n    print(fid.read())\n    fid.close()<\/code><\/pre>\n\n\n\n
In this code:<\/p>\n\n\n\n