Question 19 - Sample Paper 2 by Teachoo - Teachoo Sample Paper

Last updated at August 14, 2026 by Teachoo

What are the rules for naming an identifier in Python? Give an example of a valid and an invalid identifier

Answer:

An identifier is a name given to a variable, function, class, or module in Python.

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Some rules for naming an identifier in Python are:

It cannot be a reserved word or keyword in Python , such as if, for, while, etc.
It is case-sensitive , meaning that uppercase and lowercase letters are treated differently.

An example of a valid identifier is: _score

An example of an invalid identifier is : 2nd_name (starts with a digit)

An identifier is a name given to a variable, function, class, or module in Python. It is used to refer to the value or object associated with it.

Some rules for naming an identifier in Python are:

It can only contain letters, digits, and underscores (_). This means that other symbols such as hyphens (-), asterisks (*), or spaces are not allowed. For example, my-name is an invalid identifier because it contains a hyphen.
It cannot start with a digit. This means that numbers can be used in an identifier, but not at the beginning. For example, 2nd_name is an invalid identifier because it starts with a digit.
It cannot be a reserved word or keyword in Python, such as if, for, while, etc. These words have special meanings and functions in Python, so they cannot be used as identifiers. For example, for is an invalid identifier because it is a keyword that is used to create loops in Python.
It is case-sensitive, meaning that uppercase and lowercase letters are treated differently. This means that two identifiers that have the same spelling but different cases are considered different. For example, MAX_VALUE and max_value are two different identifiers in Python.

Some examples of valid identifiers are:

name : This is a valid identifier because it follows all the rules. It contains only letters and does not start with a digit or a keyword. It can be used to store a string value such as “Alice” or “Bob”.
age : This is another valid identifier because it follows all the rules. It contains only letters and does not start with a digit or a keyword. It can be used to store an integer value such as 18 or 25.
_score : This is also a valid identifier because it follows all the rules. It contains only letters, digits, and underscores and does not start with a digit or a keyword. The underscore at the beginning is often used to indicate that the identifier is private or internal to the code.
max_value : This is also a valid identifier because it follows all the rules. It contains only letters and underscores and does not start with a digit or a keyword. It can be used to store a numeric value such as 100 or 3.14.

Some examples of invalid identifiers are:

2nd_name : This is an invalid identifier because it starts with a digit. A possible way to fix this is to use second_name instead.
for: This is an invalid identifier because it is a keyword in Python. A possible way to fix this is to use another word such as loop or iteration instead.
my-name: This is an invalid identifier because it contains a hyphen. A possible way to fix this is to use an underscore instead of a hyphen, such as my_name.

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