{"id":80171,"date":"2021-01-09T09:00:40","date_gmt":"2021-01-09T03:30:40","guid":{"rendered":"https:\/\/techvidvan.com\/tutorials\/?p=80171"},"modified":"2021-01-09T09:00:40","modified_gmt":"2021-01-09T03:30:40","slug":"python-exec-syntax-examples","status":"publish","type":"post","link":"https:\/\/techvidvan.com\/tutorials\/python-exec-syntax-examples\/","title":{"rendered":"Python Exec() with Syntax and Examples"},"content":{"rendered":"

Do you remember that fairy basket?<\/p>\n

Nevertheless, it has so much knowledge to give, but it has one rule, one thing at a time.<\/p>\n

And today’s secret of this basket is something Dynamic.<\/p>\n

Not taking too much time to learn this new spell, here I introduce to you Exec() function, and of course, our buddy Python is going to do it all for us again. So let’s learn about Python Exec().<\/p>\n

What is Exec() function in Python?<\/h2>\n

Exec() function\u2019s usage is for the dynamic execution of a Python program, which can either be a string or object code in user-defined runtime.<\/p>\n

Do you think it is the same as Eval? Of course not.<\/p>\n

Did you read it is used for dynamic execution of code? It works on the principle of the dynamic execution of code, which makes it very different from Eval.<\/p>\n

What does this mean?<\/strong><\/p>\n

This means if it is a string, the string is parsed as a suite of Python statements and then it is executed.<\/p>\n

If it is an object code, it is simply executed in a well-defined manner for any integral value in a code.<\/p>\n

And one needs to keep in mind that the return statements may not be used outside of function definitions.<\/p>\n

Neither even within the context of code which is passed to the exec() function.<\/p>\n

This means if it is a string, it simply doesn’t return any value, hence displays ‘none’.<\/p>\n

Python Exec() Syntax<\/h3>\n

The syntax of exec() is<\/p>\n

exec(object[, globals[, locals]])\n<\/pre>\n
Like a choosy designer who accepts only perfect fabric to make a completely lavish robe, exec() does not take everything which is assigned to it.<\/p>\n
Parameters of Exec() in Python<\/h4>\n
    \n
  • Object<\/strong>: It can be a string or object code.<\/li>\n
  • Globals<\/strong>: This is a dictionary and the parameter is optional.<\/li>\n
  • Locals<\/strong>: It can be a mapping object and is also optional.<\/li>\n<\/ul>\n
    Globals and Locals Parameters in Python Exec()<\/h4>\n
    Using globals and locals parameters in user-specific codes, a coder can restrict what variables and methods the users can access in runtime.<\/p>\n
    One can either provide both or just the globals, in such a case that value suffices for both- globals and the local variables can be parsed.<\/p>\n
    At the module level, globals and locals are the same dictionaries.<\/p>\n
    Python Exec() Example<\/strong><\/p>\n
    >>> exec('print(tan(45))')\n<\/pre>\n
    Output<\/strong><\/p>\n
    >>> 1<\/div>\n
    Example of Python Exec() Function<\/b><\/p>\n
    from math import \nexec('print(fact(5))', {'fact': factorial}) \n#factorial re-coded as (fact)\n<\/pre>\n
    Output<\/strong><\/p>\n
    120<\/div>\n
    When should we use Exec in Python?<\/h3>\n
    As a side effect, implementation of exec() may insert additional keys into dictionaries.<\/p>\n
    Besides, the code corresponds to variable names and is set by the executed code.<\/p>\n
    Python Exec Example<\/strong><\/p>\n
    a=int(input(\u201center a number\u201d))\nif: \n  a= 8\n  exec('print(a==8)') \n   If true:\n  \n       exec('print(a+3)')\n<\/pre>\n
    Output<\/strong><\/p>\n
    True
    \n11<\/div>\n
    Statement Evaluation by Exec()<\/h4>\n
    Not only the integers, strings, as earlier mentioned, can get evaluated by exec() function. Here is an example of the same:<\/p>\n
    Python Exec Function Example<\/strong><\/p>\n
    for i in range(5):\\n  \nprint('Hello world!')\n<\/pre>\n
    Output<\/strong><\/p>\n
    Hello world!
    \nHello world!
    \nHello world!
    \nHello world!
    \nHello world!<\/div>\n
    Warnings while using Python Exec()<\/h4>\n
    Sometimes it happens when the coder uses a Unix system (macOS, Linux etc) or has simply imported an os module.<\/p>\n
    The os module provides a static way in user defined codes to use operating system functionalities such as the read library and appending a file.<\/p>\n
    Exec() Vs Eval() in Python<\/h3>\n
    Eval accepts a single expression while exec operates on Python statements: loops, try: except:, class and function\/method definitions in runtime.<\/p>\n
    An expression is whatever you can have as the value irrespective of its original domain in the variable assignment of the code.<\/p>\n
    Eval() returns the value of the given expression, whereas exec ignores the return value from its code, and always returns none in runtime.<\/p>\n
    Whereas in ‘eval’ mode, it compiles a single expression into the bytecode that returns user-specific value of that expression. In the ‘eval’ mode the compiler raises an exception in runtime if the source code contains statements that are user static and are also beyond a single expression for any integral value in a code in a definite runtime.<\/p>\n
    Restricting Usage of Available Methods and Variables in Exec()<\/h4>\n
    If both, parameters are being omitted for user-specific codes, the code executed by exec() is executed in the current scope location of the library having any integral or variable value.<\/p>\n
    The globals and locals parameters (basically dictionaries) are used for global and local variables respectively.<\/p>\n
    If a local dictionary is omitted, it defaults to the globals dictionary. If the coder passes an empty dictionary as globals for the search, then only the built-ins are available to the object (the first parameter to the exec()) in runtime.<\/p>\n
    Summary<\/h2>\n
    Unlike any other programming language, python has a lot to offer to its coders, with the ease and efficiency function is actually what gives its coders the best in python.<\/p>\n
    Exec() being one of them makes it so much easier for the coder to evaluate string\/integer in a simple manner.<\/p>\n
    But unlike any other function, it performs dynamic real-time execution, which can be either for a string or a code.<\/p>\n","protected":false},"excerpt":{"rendered":"
    Do you remember that fairy basket? Nevertheless, it has so much knowledge to give, but it has one rule, one thing at a time. And today’s secret of this basket is something Dynamic. Not...<\/p>\n","protected":false},"author":1,"featured_media":80173,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1053],"tags":[3340,2242,3341,3342],"class_list":["post-80171","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-python","tag-exec-in-python","tag-python","tag-python-exec","tag-python-exec-function"],"yoast_head":"\nPython Exec() with Syntax and Examples - TechVidvan<\/title>\n<meta name=\"description\" content=\"exec() function is used for dynamic execution of Python program which can either be a string or object code. 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