Python Illegal Argument Error
This module never needs to be imported explicitly: the exceptions are provided in the built-in namespace as well as the exceptions
Python Valueerror Example
module. For class exceptions, in a try statement with an python filenotfounderror except clause that mentions a particular class, that clause also handles any exception classes derived from python custom exception that class (but not exception classes from which it is derived). Two exception classes that are not related via subclassing are never equivalent, even if they have the
Python Exception Message
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 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
Python Exception Class Methods
value is the second argument to the raise statement. If the exception class is derived from the standard root 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 Python Errno of the argparse module Mathematical expressions as values Reading data from file Reading a file line by line Alternative ways python attributeerror object has no attribute of reading a file The modern with statement The old while construction Reading a file into a string Reading a mixture of text and numbers Is it more to file reading? Writing https://docs.python.org/2/library/exceptions.html data to file Example: Writing a table to file Problem Solution Standard input and output as file objects Redirecting standard input, output, and error Note What is a file, really? Pure text files Word processor files Image files Music files PDF files Remarks Handling errors Exception handling Testing for a specific exception Examples on exception types Digression Raising exceptions Example A glimpse of graphical http://hplgit.github.io/primer.html/doc/pub/input/._input-readable007.html user interfaces Making modules Example: Interest on bank deposits Collecting functions in a module file Test block Example on a test block in a minimalistic module A test block in the interest module Verification of the module code Getting input data Doc strings in modules Using modules What gets imported by various import statements? How to make Python find a module file How to make Python run the module file Distributing modules Making software available on the Internet Making code for Python 2 and 3 Basic differences between Python 2 and 3 The print statement has changed Integer division is not an issue in Python 3 The raw_input function is named input in Python 3 Turning Python 2 code into Python 3 code Summary Chapter topics Question and answer input Getting command-line arguments Using option-value pairs Generating code on the fly Turning string formulas into Python functions File operations Handling exceptions Raising exceptions Modules Terminology Example: Bisection root finding Problem Solution Verification Making a function Making a test function Making a module Defining a user interface Using the module Potential problems with the software Distributing the bisection module to others Exercises Exerci
topic Dictionaries and Tuples Next topic Functions This Page Show Source Quick search Enter search terms or a module, class or function name. Errors (also called Exceptions)¶ Introduction¶ When something goes wrong, Python responds by giving you a rude message that http://www.openbookproject.net/pybiblio/gasp/course/E-errors.html might look something like this: Traceback (innermost last): File "", line 1, in ? File http://www.programiz.com/python-programming/exceptions "", line 1, in f TypeError: illegal argument type for built-in operation You can usually ignore everything except the last line, although the earlier lines may - if you look at them closely - give some hints about where the trouble happened. This sheet is a brief guide to some of the commoner things you might see on that last python exception line, what they mean and what you might have done to provoke them. Error messages¶ Attribute Errors, Key Errors, Index Errors¶ These have messages starting AttributeError: , KeyError: or IndexError: . They all mean something rather similar: you were trying to get at a part of an object (one element of a list, for instance), but you asked for a non-existent part of the object. So, if x is the list [1, 2, 3] python illegal argument and you ask for x[100] you'll get an IndexError. Name Errors¶ These all have messages starting NameError: . They mean I've never heard of this thing . The thing Python's never heard of is what comes after NameError: . This might mean that you mistyped something: primt x instead of print x, say. It might also mean that you used a variable (i.e., a name) before it was defined. Or that you used a function before it was defed. One way this can sometimes happen is if you forget the quotation marks around a string. Syntax Errors¶ These all have messages starting SyntaxError: . What they have in common is that you said something Python couldn't even begin to make sense of. If someone says I apple eat like the to then that's a syntax error! SyntaxError: invalid syntax This can mean lots of things. Here are some examples of things that provoke it. + + + # Add *what* to *what*? 1z6 # Is it a number? Is it a variable? Is it a mistake? for # After ``for`` there ought to be some more stuff while if: # ``if`` isn't a thing that can be true or false! def 1(x): # ``1`` is a number. You can't use it as a name for a function f([) # The ``[``
that are built-in in Python. When writing a program, we, more often than not, will encounter errors. Error caused by not following the proper structure (syntax) of the language is called syntax error or parsing error. >>> if a < 3 File "", line 1 if a < 3 ^ SyntaxError: invalid syntax We can notice here that a colon is missing in the if statement. Errors can also occur at runtime and these are called exceptions. They occur, for example, when a file we try to open does not exist (FileNotFoundError), dividing a number by zero (ZeroDivisionError), module we try to import is not found (ImportError) etc. Whenever these type of runtime error occur, Python creates an exception object. If not handled properly, it prints a traceback to that error along with some details about why that error occurred. >>> 1 / 0 Traceback (most recent call last): File "", line 301, in runcode File "", line 1, in ZeroDivisionError: division by zero >>> open("imaginary.txt") Traceback (most recent call last): File "", line 301, in runcode File "", line 1, in FileNotFoundError: [Errno 2] No such file or directory: 'imaginary.txt' Python Built-in Exceptions Illegal operations can raise exceptions. There are plenty of built-in exceptions in Python that are raised when corresponding errors occur. We can view all the built-in exceptions using the local() built-in functions as follows. >>> locals()['__builtins__'] This will return us a dictionary of built-in exceptions, functions and attributes. Some of the common built-in exceptions in Python programming along with the error that cause then are tabulated below. Python Built-in Exceptions Exception Cause of Error AssertionError Raised when assert statement fails. AttributeError Raised when attribute assignment or reference fails. EOFError Raised w