Python Errors and Built-in Exceptions
In this tutorial, you will find out about various sorts of errors and exceptions that are built-in Python. They are raised at whatever point the Python interpreter encounters errors.
We can make certain mistakes while writing a program that leads to blunders when we attempt to run it. A python program ends when it experiences an unhandled mistake. These mistakes can be extensively characterized into two classes:
1. Syntax errors
2. Logical errors (Exceptions)
Python Syntax Errors
Mistake brought about by not following the correct structure (linguistic structure) of the language is called punctuation blunder or parsing error.
Let’s look at one example:
>>> if a < 3 File "<interactive input>", line 1 if a < 3 ^ SyntaxError: invalid syntax
As shown in the example, an arrow indicates where the parser ran into the syntax error.
We can notice here that a colon: is missing in the if statement.
Python Logical Errors (Exceptions)
Errors that happen at runtime (in the wake of breezing through the linguistic structure assessment) are called exceptions or logical errors.
For example, they happen when we attempt to open a file(for perusing) that doesn’t exist (FileNotFoundError), attempt to separate a number by zero (ZeroDivisionError) or attempt to import a module that doesn’t exist (ImportError).
Whenever these sorts of runtime errors happen, Python makes an exception object. If not taken care of appropriately, it prints a traceback to that blunder alongside certain insights regarding why that error occurred.
Let’s look at how Python treats these errors:
>>> 1 / 0 Traceback (most recent call last): File "<string>", line 301, in runcode File "<interactive input>", line 1, in <module> ZeroDivisionError: division by zero >>> open("imaginary.txt") Traceback (most recent call last): File "<string>", line 301, in runcode File "<interactive input>", line 1, in <module> FileNotFoundError: [Errno 2] No such file or directory: 'imaginary.txt'
Python Built-in Exceptions
Illegal operations can raise special cases. There are plenty of built-in exceptions in Python that are raised while comparing blunders happen. We can see all the inherent special cases using the built-in local() function as follows:
locals()[‘__builtins__’] will return a module of built-in exceptions, functions, and attributes. dir allows us to list these attributes as strings.
Some of the common built-in exceptions in Python programming along with the error that causes them are listed below:
|Exception||Cause of Error|
|AssertionError||Raised when an assert statement fails.|
|AttributeError||Raised when attribute assignment or reference fails.|
|EOFError||Raised when the input() function hits end-of-file condition.|
|FloatingPointError||Raised when a floating-point operation fails.|
|GeneratorExit||Raise when a generator’s close() method is called.|
|ImportError||Raised when the imported module is not found.|
|IndexError||Raised when the index of a sequence is out of range.|
|KeyError||Raised when a key is not found in a dictionary.|
|KeyboardInterrupt||Raised when the user hits the interrupt key (Ctrl+C or Delete).|
|MemoryError||Raised when an operation runs out of memory.|
|NameError||Raised when a variable is not found in the local or global scope.|
|NotImplementedError||Raised by abstract methods.|
|OSError||Raised when system operation causes the system-related error.|
|OverflowError||Raised when the result of an arithmetic operation is too large to be represented.|
|ReferenceError||Raised when a weak reference proxy is used to access a garbage collected referent.|
|RuntimeError||Raised when an error does not fall under any other category.|
|StopIteration||Raised by next() function to indicate that there is no further item to be returned by the iterator.|
|SyntaxError||Raised by the parser when a syntax error is encountered.|
|IndentationError||Raised when there is incorrect indentation.|
|TabError||Raised when indentation consists of inconsistent tabs and spaces.|
|SystemError||Raised when the interpreter detects the internal error.|
|SystemExit||Raised by sys.exit() function.|
|TypeError||Raised when a function or operation is applied to an object of the incorrect type.|
|UnboundLocalError||Raised when a reference is made to a local variable in a function or method, but no value has been bound to that variable.|
|UnicodeError||Raised when a Unicode-related encoding or decoding error occurs.|
|UnicodeEncodeError||Raised when a Unicode-related error occurs during encoding.|
|UnicodeDecodeError||Raised when a Unicode-related error occurs during decoding.|
|UnicodeTranslateError||Raised when a Unicode-related error occurs during translating.|
|ValueError||Raised when a function gets an argument of correct type but improper value.|
|ZeroDivisionError||Raised when the second operand of division or modulo operation is zero.|
If required, we can also define our own exceptions in Python. To learn more about them, visit Python User-defined Exceptions.
We can handle these built-in and user-defined exceptions in Python using try, except and finally statements. To learn more about them, visit Python try, except and finally statements.
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