Identifiers in python programming

In Python, an identifier is a name given to a variable, function, class, or module. It is used to identify the entity in the program.

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An identifier can contain letters (both uppercase and lowercase), numbers, and underscore (_). However, it cannot start with a number. Here are some rules for naming an identifier in Python:

1. An identifier must begin with a letter or an underscore (_).
2. An identifier cannot start with a number.
3. An identifier can only contain alphanumeric characters (letters and numbers) and underscores (_).
4. Identifiers are case-sensitive, meaning that “myVar” and “myvar” are two different identifiers.
5. Python has some reserved words that cannot be used as an identifier. These reserved words include keywords like “if,” “else,” “for,” “while,” and “class.”

Examples of valid identifiers in Python:

my_var = 10
myVar = 20
_myvar = 30
myVar123 = 40

Examples of invalid identifiers in Python:

1myvar = 10     # Cannot start with a number
my-var = 20     # Cannot contain a hyphen
my var = 30     # Cannot contain a space
if = 40         # Cannot use a reserved keyword as an identifier