{"id":79304,"date":"2020-07-05T09:00:49","date_gmt":"2020-07-05T03:30:49","guid":{"rendered":"https:\/\/techvidvan.com\/tutorials\/?p=79304"},"modified":"2020-07-05T09:00:49","modified_gmt":"2020-07-05T03:30:49","slug":"errors-and-exceptions-in-python","status":"publish","type":"post","link":"https:\/\/techvidvan.com\/tutorials\/errors-and-exceptions-in-python\/","title":{"rendered":"Errors and Exceptions in Python"},"content":{"rendered":"

No matter how good you make your code<\/strong>, things can go wrong.<\/p>\n

When we plan our program<\/strong>, we always work for situations<\/strong> we normally expect. And our program works<\/strong> quite well in those situations<\/strong>. But we often ignore<\/strong> the possibility<\/strong> of unexpected situations<\/strong> which can mess<\/strong> with the normal execution<\/strong> of our program<\/strong>.<\/p>\n

Let\u2019s learn about such situations<\/strong> and what exactly happens when our program encounters Python error<\/strong> and exception<\/strong>.<\/p>\n

Python Error<\/h3>\n

You might have come across syntax<\/strong> errors<\/strong> millions of times in your initial stages<\/strong> of learning Python<\/strong>. Everybody does. And even if your syntax<\/strong> is correct<\/strong>, you might encounter errors<\/strong> while execution<\/strong> of your program<\/strong>.<\/p>\n

Errors<\/strong> are unusual<\/strong> and unexpected situations<\/strong> that affect the normal flow<\/strong> of program execution<\/strong>. We make errors<\/strong> all the time.<\/p>\n

Some of these errors are \u201ccompile-time\u201d<\/strong> errors<\/strong>. These errors occur before the program execution begins, i.e., at the<\/strong> time of compilation<\/strong>.<\/p>\n

While the other errors are \u201crun-time\u201d<\/strong> errors and occur after the code<\/strong> is successfully<\/strong> compiled<\/strong> and is running<\/strong>.<\/p>\n

The two distinguishable<\/strong> types of errors in Python are:<\/p>\n

    \n
  • Syntax errors –<\/strong> Compile-time error<\/li>\n
  • Exceptions –<\/strong> Run-time errors<\/li>\n<\/ul>\n

    Let\u2019s have a look at Syntax errors before talking about the \u2018elephant in the room\u2019<\/strong>– Exceptions.<\/p>\n

    Python Syntax Error<\/h3>\n

    A syntax error<\/strong> occurs when you don\u2019t follow proper rules<\/strong> and structure<\/strong> of the language<\/strong>. A very common mistake that we make while getting accustomed<\/strong> to Python\u2019s syntax is not using correct indentation<\/strong>. This results in a syntax error<\/strong>.<\/p>\n

    Another example would be not putting a colon<\/strong> after a function header<\/strong>, or not enclosing<\/strong> a string within quotes<\/strong>.<\/p>\n

    >>> l = [1, 2, 3]\n\n>>> for i in l\nSyntaxError: invalid syntax\n>>> \n\n<\/pre>\n
    Recognize the error<\/strong> here?<\/p>\n
    We forgot to put a colon after \u201cfor i in l\u201d<\/strong>. And as we press Enter<\/strong> to start the for-loop\u2019s<\/strong> block, we get a SyntaxError<\/strong> message.<\/p>\n
    There are so many places in your code<\/strong> where you can possibly go wrong<\/strong>. And as soon as the compiler recognizes<\/strong> your mistake<\/strong>, it pops up<\/strong> a syntax error message<\/strong>.<\/p>\n
    Your program<\/strong> will not start executing<\/strong> until you correct <\/strong>all the syntax errors<\/strong> in your code<\/strong>.<\/p>\n
    Python Exceptions<\/h3>\n
    Even if you get the syntax<\/strong> right<\/strong>, your program might get stuck somewhere<\/strong> during execution<\/strong>. This is due to the errors<\/strong> in your code<\/strong> which occur at run-time<\/strong>. There is no way for your compiler<\/strong> to recognize<\/strong> such errors<\/strong>.<\/p>\n
    Exceptions<\/strong> in python are the errors<\/strong> that occur during execution<\/strong>. Well simply put, exceptions occur<\/strong> when your program<\/strong> tries<\/strong> to perform<\/strong> an operation<\/strong> it wasn\u2019t supposed to. This is when your program crashes<\/strong> and the interpreter displays<\/strong> a runtime exception<\/strong> message<\/strong> on the screen<\/strong>.<\/p>\n
    There are many different circumstances<\/strong> under which your Python program<\/strong> might crash<\/strong>.<\/p>\n
    In fact, Python\u2019s interpreter<\/strong> comes up with a complete list<\/strong> of built-in <\/strong>exception types<\/strong>.<\/p>\n
    Common Python Exceptions<\/h3>\n
    You\u2019ll find some of the common exceptions in the table below.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
    Exception<\/b><\/td>\nWhy it gets raised<\/b><\/td>\n<\/tr>\n
    AssertionError<\/span><\/td>\nWhen an assert statement<\/strong> fails<\/strong>.<\/span><\/td>\n<\/tr>\n
    AttributeError<\/span><\/td>\nWhen an attribute reference<\/strong> or assignment<\/strong> fails.<\/span><\/td>\n<\/tr>\n
    EOFError<\/span><\/td>\nWhen input() function encounters End Of File(EOF)<\/strong>.<\/span><\/td>\n<\/tr>\n
    FloatingPointError<\/span><\/td>\nWhen an operation on floating-point<\/strong> fails.<\/span><\/td>\n<\/tr>\n
    ImportError<\/span><\/td>\nWhen a module you want to import<\/strong> is not found.<\/span><\/td>\n<\/tr>\n
    IndexError<\/span><\/td>\nWhen you try to access the element<\/strong> at an index which is out of range.<\/span><\/td>\n<\/tr>\n
    KeyError<\/span><\/td>\nWhen a key is not present in a dictionary<\/strong>.<\/span><\/td>\n<\/tr>\n
    KeyboardInterrupt<\/span><\/td>\nWhen the user presses the interrupt key(Control-c or Delete)<\/strong>.<\/span><\/td>\n<\/tr>\n
    MemoryError<\/span><\/td>\nWhen an operation runs out of memory<\/strong>.<\/span><\/td>\n<\/tr>\n
    NameError<\/span><\/td>\nWhen a variable is not found in scope<\/strong>.<\/span><\/td>\n<\/tr>\n
    NotImplementedError<\/span><\/td>\nWhen an abstract<\/strong> method is not implemented anywhere in the code.<\/span><\/td>\n<\/tr>\n
    OSError<\/span><\/td>\nWhen a system-related<\/strong> error occurs.<\/span><\/td>\n<\/tr>\n
    OverflowError<\/span><\/td>\nWhen an arithmetic operation<\/strong> produces a really large result<\/span><\/td>\n<\/tr>\n
    RuntimeError<\/span><\/td>\nWhen a run-time<\/strong> error doesn\u2019t fall in any of the other categories.<\/span><\/td>\n<\/tr>\n
    StopIteration<\/span><\/td>\nThe <\/span>next()<\/strong> function raises it when there are no more elements in the iterable.<\/span><\/td>\n<\/tr>\n
    SyntaxError<\/span><\/td>\nWhen there is an error in the syntax<\/strong>.<\/span><\/td>\n<\/tr>\n
    IndentationError<\/span><\/td>\nWhen the indentation<\/strong> is not correct.<\/span><\/td>\n<\/tr>\n
    TabError<\/span><\/td>\nInconsistent tabs and spaces in the indentation. It is a subclass of <\/span>IndentationError<\/strong>.<\/span><\/td>\n<\/tr>\n
    SystemError<\/span><\/td>\nWhen the interpreter detects an internal error<\/strong>.<\/span><\/td>\n<\/tr>\n
    TypeError<\/span><\/td>\nWhen an operation or function tries to operate on an object of the incorrect type<\/strong>.<\/span><\/td>\n<\/tr>\n
    UnboundLocalError<\/span><\/td>\nWhen you reference a local variable before assigning<\/strong> it a value.<\/span><\/td>\n<\/tr>\n
    ValueError<\/span><\/td>\nWhen you pass an object of correct type but the improper<\/strong> value to a function.<\/span><\/td>\n<\/tr>\n
    ZeroDivisionError<\/span><\/td>\nWhen the second operand of a division or modulo operator is zero<\/strong>.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
    Summary<\/h3>\n
    In this Python error article by TechVidan, we saw what Python error<\/strong> is and how it can affect the normal flow<\/strong> of execution<\/strong> of our program<\/strong>. We also learned about Python exceptions<\/strong> and their types<\/strong>.<\/p>\n
    A good program<\/strong> should be able to handle<\/strong> any exception<\/strong> that may possibly occur<\/strong>. We\u2019ll learn how to handle<\/strong> these exceptions<\/strong> in another article.<\/p>\n
    Till then, keep coding<\/strong> and be careful of those errors<\/strong>!<\/p>\n","protected":false},"excerpt":{"rendered":"
    No matter how good you make your code, things can go wrong. When we plan our program, we always work for situations we normally expect. And our program works quite well in those situations....<\/p>\n","protected":false},"author":1,"featured_media":79378,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1053],"tags":[3000,3001,3002],"class_list":["post-79304","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-python","tag-errors-and-exceptions-in-python","tag-python-error","tag-python-exception"],"yoast_head":"\nErrors and Exceptions in Python - TechVidvan<\/title>\n<meta name=\"description\" content=\"Learn what is Python error with example, types of Errors in python-syntax errors and exception, types of exception and when they are raised.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/techvidvan.com\/tutorials\/errors-and-exceptions-in-python\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Errors and Exceptions in Python - 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