{"id":74272,"date":"2019-12-16T14:30:21","date_gmt":"2019-12-16T09:00:21","guid":{"rendered":"https:\/\/techvidvan.com\/tutorials\/?p=74272"},"modified":"2024-08-22T17:56:56","modified_gmt":"2024-08-22T12:26:56","slug":"python-identifiers","status":"publish","type":"post","link":"https:\/\/techvidvan.com\/tutorials\/python-identifiers\/","title":{"rendered":"Python Identifiers &#8211; Learn to name variables in Python"},"content":{"rendered":"<p>In this TechVidvan&#8217;s Python article, we are going to learn about identifiers in Python. They are the basic building blocks of Python and we use them everywhere while writing programs. So, it\u2019s important to understand everything about them.<\/p>\n<p>We will see the <strong>rules<\/strong> to define <strong>identifiers<\/strong>, and all the best practices to follow while defining Python identifiers. Let\u2019s start with the definition of identifiers.<\/p>\n<h3>What is Python Identifier?<\/h3>\n<p>&#8220;An identifier is a name given to an entity&#8221;.<\/p>\n<p>In very simple words, an identifier is a user-defined name to represent the basic building blocks of Python. It can be a <strong>variable<\/strong>, a <strong>function<\/strong>, a <strong>class<\/strong>, a <strong>module<\/strong>, or any other object.<\/p>\n<h4>Naming Rules for Identifiers<\/h4>\n<p>Now you know what exactly identifiers are. So, how do we use them? We can\u2019t use anything, there are some certain <strong>rules<\/strong> to keep in mind that we must follow while naming identifiers.<\/p>\n<p>1. The Python identifier is made with a <strong>combination<\/strong> of <strong>lowercase<\/strong> or <strong>uppercase<\/strong> <strong>letters<\/strong>, <strong>digits<\/strong> or an <strong>underscore<\/strong>.<\/p>\n<p>These are the valid characters.<\/p>\n<ul>\n<li>Lowercase letters (a to z)<\/li>\n<li>Uppercase letters (A to Z)<\/li>\n<li>Digits (0 to 9)<\/li>\n<li>Underscore (_)<\/li>\n<\/ul>\n<p><strong>Examples of a valid identifier:<\/strong><\/p>\n<ul>\n<li>num1<\/li>\n<li>FLAG<\/li>\n<li>get_user_name<\/li>\n<li>userDetails<\/li>\n<li>_1234<\/li>\n<\/ul>\n<p>2. An identifier cannot start with a <strong>digit<\/strong>. If we create an identifier that starts with a digit then we will get a <strong>syntax error<\/strong>.<\/p>\n<p><strong>Example:<\/strong><a href=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/invalid-identifiers.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"img-gray-border aligncenter wp-image-74416 size-full\" src=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/invalid-identifiers.jpg\" alt=\"invalid identifiers in python\" width=\"1366\" height=\"728\" \/><\/a><\/p>\n<p>3. We also cannot use<strong> special symbols<\/strong> in the identifiers name.<\/p>\n<p>Symbols like<strong> ( !, @, #, $, %, . )<\/strong> are invalid.<\/p>\n<p><strong>Example:<\/strong><a href=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/Invalid-Identifiers-1.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"img-gray-border aligncenter wp-image-74417 size-full\" src=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/Invalid-Identifiers-1.jpg\" alt=\"identifiers in python\" width=\"1366\" height=\"728\" \/><\/a><\/p>\n<p>4. A keyword cannot be used as an <strong>identifier<\/strong>. In Python, keywords are the <strong>reserved names<\/strong> that are built-in in Python. They have a special meaning and we cannot use them as identifier names.<a href=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/Invalid-Identifiers-2.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"img-gray-border aligncenter wp-image-74418 size-full\" src=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/Invalid-Identifiers-2.jpg\" alt=\"python identifiers\" width=\"1366\" height=\"728\" \/><\/a><\/p>\n<p>If you want to see the list of all the keywords, then in your Python shell, type<strong> \u201chelp()\u201d<\/strong> and then type <strong>\u201ckeywords\u201d<\/strong> to get the list of all Python keywords.<a href=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/reseved-keywords-in-python.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"img-gray-border aligncenter wp-image-74419 size-full\" src=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/reseved-keywords-in-python.jpg\" alt=\"python reserved keywords\" width=\"1366\" height=\"728\" \/><\/a><\/p>\n<p>5. The <strong>length<\/strong> of the identifiers can be as long as you want. Of course, it can not be greater than the available memory, however, the <strong>PEP-8<\/strong> standards rule suggests not to exceed <strong>79<\/strong> characters in a line.<\/p>\n<h3>Testing the Validity of Python Identifiers<\/h3>\n<p>Python has some helper functions that are useful when you are not sure whether a <strong>string<\/strong> is a <strong>keyword<\/strong> or a <strong>valid identifier<\/strong>.<\/p>\n<p>1. To check whether a <strong>string<\/strong> is a <strong>keyword<\/strong> or not, we have a keyword module.<\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"null\">import keyword\r\nprint( keyword.iskeyword(\u201cvar\u201d) )\r\nprint( keyword.iskeyword(\u201cFalse\u201d) )\r\nprint( keyword.iskeyword(\u201ccontinue\u201d) )\r\nprint( keyword.iskeyword(\u201ccount\u201d) )<\/pre>\n<p><strong>Output:<\/strong><\/p>\n<div class=\"code-output\">False<br \/>\nTrue<br \/>\nTrue<br \/>\nFalse<\/div>\n<p>2. The <strong>str.isidentifier()<\/strong> function is used to check the <strong>validity<\/strong> of an identifier.<\/p>\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"null\">print( \u201cname\u201d.isidentifier() )\r\nprint( \u201c#today\u201d.isidentifier() )\r\nprint( \u201c_12hello\u201d.isidentifier() )\r\nprint( \u201c8cellos\u201d.isidentifier() )<\/pre>\n<p><strong>Output:<\/strong><\/p>\n<div class=\"code-output\">True<br \/>\nFalse<br \/>\nTrue<br \/>\nFalse<\/div>\n<h3>Best Practices for Python Identifiers<\/h3>\n<p>Following the naming conventions are mandatory for everyone. But that\u2019s not it!<\/p>\n<p>The Python community has made a few more <strong>guidelines<\/strong> that are not compulsory but it is advised to follow some practices that are better for everyone in understanding things. Let\u2019s see what these guidelines are.<\/p>\n<p>1. Class names should start with a <strong>capital<\/strong> <strong>letter<\/strong> and all the other identifiers should start with a <strong>lowercase letter<\/strong>.<\/p>\n<p>2. Begin private identifiers with an <strong>underscore (_)<\/strong>. Note, this is not needed to make the <strong>variable private<\/strong>. It is only for the ease of the programmer to easily distinguish between <strong>private variables<\/strong> and <strong>public variables<\/strong>.<\/p>\n<p>3. Use <strong>double underscores (__)<\/strong> around the names of magic methods and don\u2019t use them anywhere else. Python built-in magic methods already use this notation. <strong>For example:<\/strong> __init__ , __len__ .<\/p>\n<p>4. Double underscores are used only when you are dealing with <strong>mangling<\/strong> in Python.<\/p>\n<p>5. Always prefer using names longer than one character. <strong>index=1<\/strong> is better than <strong>i=1<\/strong><\/p>\n<p>6. To combine words in an <strong>identifier<\/strong>, you should use <strong>underscore(_)<\/strong>. <strong>For example:<\/strong>\u00a0get_user_details.<\/p>\n<p>7. Use camel case for naming the variables. <strong>For example:<\/strong> fullName, getAddress, testModeOn, etc.<\/p>\n<h3>Reserved Classes of Python Identifiers<a href=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/reserved-classes-of-python-identifiers-1.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-74356 size-full\" src=\"https:\/\/techvidvan.com\/tutorials\/wp-content\/uploads\/sites\/2\/2019\/12\/reserved-classes-of-python-identifiers-1.jpg\" alt=\"reserved classes of python identifiers\" width=\"594\" height=\"448\" \/><\/a><\/h3>\n<p>Some classes in Python have special meanings and to identify them, we use patterns of leading and trailing underscores.<\/p>\n<h4>1. Single leading underscore (_*)<\/h4>\n<p>This identifier is often used to store the result of the last evaluation in the interactive interpreter, specifically stored in the __builtin__ module. Variables with a single leading underscore are considered private and are not imported when you use the &#8220;from module import *&#8221; statement.<\/p>\n<h4>2. Double leading and trailing underscores (__*__)<\/h4>\n<p>These identifiers are reserved for system-defined names. They are defined by the interpreter and its implementations, and it\u2019s not recommended to create additional names using this convention. Examples include special methods like __init__ or __str__.<\/p>\n<h4>3. Leading double underscores (__*)<\/h4>\n<p>These identifiers are used for class-private name mangling. Within the context of a class definition, names with leading double underscores are rewritten to avoid name clashes between private variables in base and derived classes. This ensures that these private variables remain private to the class and do not interfere with other parts of the code.<\/p>\n<h3>Summary<\/h3>\n<p>This is all about the <strong>Python identifiers<\/strong>.<\/p>\n<p>To sum everything up, we understood how the basic building blocks, Python identifiers, are named. We discussed the rules to define an identifier and all the best practices that every good Python programmer follows. Also, we discussed the reserved classes in Python Identifiers.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In this TechVidvan&#8217;s Python article, we are going to learn about identifiers in Python. They are the basic building blocks of Python and we use them everywhere while writing programs. 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