Identifiers in Python | Python Keywords and Identifiers Syntax & Rules



Know Python Identifiers and its Syntax. Follow Python Syntax of Identifiers and Rules. Get the Basic Block of Python which is Identifiers. Identifiers in Python helps you in representing the syntax and structure of the Python. Check the below sections to get the complete details regarding the Identifiers in Python and also its Syntax and Rules to make the programming successful.

Python Identifiers

The name in Python language is called Identifier. Identifiers may be of variable name, class name or method name. To define several variables, classes or methods you require name which is used as Identifier in Python. To define the identifiers in Python, you have to follow some of the certain rules and regulations to avoid the errors in Programming. If the conventions are not followed, then Python Interpreter throws error.

Example 1: if x=10, then x is the identifier because it is used as a name to identify 10.

Example 2: If def f1():

pass, then f1 is the identifier because it is the function used as the name to identify del function.

Example 3: If class Test(Exception);

Test is the identifier, which is the name used to identify the method name.

Rules to define Identifiers in Python

Rule 1: Symbols allowed in Python:

Python programming language allows only certain symbols to define identifiers. It is mandatory to use only those symbols to make a error free program.

  1. Alphabet Symbols: Python Identifiers allows all the alphabet symbols, both upper case and lower case (e.g., A,B,C,a,b,c)
  2. Digits: Identifiers in Python allows digits i.e., 0 to 9.
  3. Underscore: Identifiers of Python language accepts underscore symbols for defining them i.e., (_).

These are the symbols where the Python language allows to define its identifiers. Other than the above mentioned symbols, no other symbol can be used to define identifiers in Python. If any other symbol is used other than these, Python Interpreter throws an error and the program cannot be executed. In Java, $ symbol is allowed whereas it is not accepted in Python language. $ symbol is not allowed because the internal style is implemented without $ symbol.


>>> cash=10



>>>ca$h= 10

Syntax Error: Invalid Syntax

Rule 2: Should not start with digit

The rule is that Python programming language Identifiers should not start with digits. The Identifiers can start with alphabets (both uppercase and lowercase), underscore (_) but not with digits.


total 123=10


Syntax Error: Invalid Syntax

Rule 3: Case Sensitive

Python language Identifiers are case sensitive. It means that upper letter alphabets are lower letter alphabets are considered separately. You can define two variables one with upper case letter and other with lower case letter.



>>> TOTAL = 20





Rule 4: Keywords cannot be used as Identifiers

In Python programming language, keywords cannot be used as identifiers. Check the example given in the below section.





Syntax Error: Invalid Syntax

>>> def =20

Syntax Error: Invalid Syntax

Rule 5: Maximum length of identifiers

In Python Programming language, the identifiers allows upto n length of characters which means that there is no limit for the Python identifiers. But it is not recommended to take the too lengthy identifier as it effects the readability. But no error occurs if the identifier is lengthy.


>>>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx = 10


It effects the readability but no error occurs.

Factors of Python Identifiers

  1. If the Identifier starts with underscore(_) symbol it indicates it as “private”.
  2. If the Python Identifier starts with double underscore (__) symbol it indicates it as : strongly private. You can know about strongly private in OOPS concepts.
  3. If the Identifier of the Python language starts with double underscore and ends with double underscore (__main__) it indicates language specific identifier. It is the special variable defined by Python itself. These concept can be used in overloaded operators.

Python Reserved Words

Know the Python Reserved Words. Check the various Python Reserved Words and its types. Also, know what are the Python Reserved Words. Follow the below sections to know the Types & Kinds of the Reserved Words in Python programming Language.

In Python programming language,some of the words are reserved to represent the functionality or meaning which are called reserved words. Most of the people have a question regarding the Reserved Words in Python i.e., How many Reserved Words does Python language consists of? We are providing the solution for your answer in the below sections. Know the functionality and syntax of the reserved words. There are 33 Reserved Words in Python.

33 Reserved Words:

  • True
  • False
  • None
  • and
  • or
  • not
  • is
  • if
  • else
  • elif
  • while
  • for
  • break
  • continue
  • return
  • in
  • yield
  • try
  • except
  • finally
  • raise
  • assert
  • import
  • from
  • as
  • class
  • def
  • pass
  • global
  • nonlocal
  • lambda
  • del
  • with

Important Points regarding Reserved Words in Python

There is a common point in all the 33 reserved words i.e., All the Python Reserved Words contains only alphabet symbols.
Except True, False and None, every other reserved words contains only lower case alphabet symbol.

Example 1:

>>>a= True



>>> a =true

>>> a

Traceback (most recent call last):

File “<pyshell|2>”, line 1, in <module>


NameError: name ‘true’ is not defined

Example 2:

>>> a = None

>>> a


>>> a = none

>>> a

Traceback (most recent call last):

File “<pyshell|2>”, line 1, in <module>


NameError: name ‘none’ is not defined

Individuals who are learning the Python language for the first time can make use of this guide. This guide will help you to clear all our doubts regarding the Python language. For the best Online Training in Hyderabad, check Panditlink. Make use of the Beginners Guide for Python language and clarify all your doubts. Know the various details regarding Python language and check this site for regular updates. Bookmark this page for the updates regarding various languages like Python, RPA UI Path, SQL Server, Angular JS, Selenium etc.

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