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Identifier in Python

Last Updated on October 16, 2023 by Ankit Kochar

In the realm of computer programming, an identifier serves as a designation for elements within the code, such as variables, functions, classes, modules, and more. The criteria governing the creation of legitimate identifiers differ among programming languages but generally involve commencing with a letter or underscore, followed by combinations of letters, digits, and underscores. Certain programming languages also impose restrictions on identifier length. In the context of Python, we delve into Python identifiers, the rules dictating their formation, and examples of both valid and invalid Python identifiers. It’s worth noting that some reserved words, like "class" in Python, are off-limits for use as identifiers.

What is Identifier?

An identifier is the term assigned to a variable, class, module, function, or any other element within code, serving as a reference to these program components. In Python, naming rules for identifiers require them to begin with a letter or underscore, followed by letters, underscores, or digits. Additionally, it’s essential to avoid using reserved words as identifiers. Identifiers must possess uniqueness and convey meaning, contributing to code clarity and understanding. They exhibit case sensitivity, distinguishing between "variable" and "Variable." The scope of identifiers can be either local or global, dictating their accessibility within the program.

What is Identifier in Python?

Identifiers in Python is a names used to identify a variable, function, class, module, or other objects. An identifier can only contain letters, digits, and underscores, and cannot start with a digit. In Python, identifiers are case-sensitive, meaning that foo and Foo are considered to be two different identifiers.

Examples of Python Identifiers

Here we have some examples of valid and invalid identifiers in python

Valid Identifiers
These are examples of valid identifiers in python.

  • yourname It contains only lowercase alphabets.
  • Name_school It contains only ‘_’ as a special character.
  • Id1 Here, the numeric digit comes at the end.
  • roll_2 It starts with lowercase and ends with a digit.
  • _classname Contains lowercase alphabets and an underscore and It starts with an underscore ‘_’

Invalid Identifiers
These are examples of valid invalid identifiers in python.

  • (for, while, in)These are the keywords in python that cannot use as identifiers in python.
  • 1myname Invalid identifier because It begins with a digit
  • \$myname Invalid identifier because It starts with a special character
  • a b Invalid identifier because it contains a blank space
  • (a/b and a+b) are Invalid identifiers because contain special character

Rules for Identifiers in Python

These are the rules for identifiers in python

  • Keywords cannot be used as identifiers in python (because they are reserved words)
  • The name of identifiers in python cannot begin with a number
  • All the identifiers in python should have a unique name in the same scope
  • The first character of identifiers in python should always start with an alphabet or underscore, and then it can be followed by any of the digit, character, or underscore.
  • Identifier name length is unrestricted
  • Names of identifiers in python are case sensitive meaning ‘car’ and ‘Car’
  • Would be treated differently
  • Special characters such as ‘%’, ‘#’,’@’, and ‘$’ are not allowed as identifiers in python.

Python Identifier Naming

When naming identifiers in python, it is recommended to follow these best practices:

  • Use descriptive and meaningful names: names should accurately describe the purpose of the identifier, and make it easy to understand the code.
  • Use snake_case: in Python, it is recommended to use snake_case instead of camelCase or PascalCase for naming variables, functions, and methods.
  • Avoid using Python keywords: keywords like if, else, def, etc. cannot be used as names for identifiers.
  • Avoid using abbreviations: abbreviations can make the code harder to read and understand.
  • Limit the length of names: names should be short and concise, but not too short to the point of being ambiguous.
  • Use consistent naming conventions: be consistent in your naming conventions throughout the codebase to improve readability and maintainability.
  • Identifiers in python should be descriptive and meaningful. For example, "x" is not a good variable name, but "student_name" is more informative.
  • Identifiers in python should be lowercase and use underscores to separate words. This convention is known as show_case.
  • It is not recommended to use special characters and spaces in an identifier name.
  • It’s a good practice to avoid using single-letter variable names except for temporary variables in python
  • Some library/module names also follow the same naming conventions, it is a good practice to follow the same for your identifier.

Identifiers in Python are pivotal components of code, serving as names for variables, classes, modules, functions, and more. Adhering to specific naming rules, ensuring uniqueness, and conveying meaningfulness are essential when creating identifiers. Their case sensitivity and scope, whether local or global, greatly influence their functionality within a Python program.

Frequently Asked Questions(FAQ) on Identifiers in Python

Here are the some frequently asked questions and answers on identifiers in python the question-and-answer form:

1. Why are meaningful and unique identifiers important in Python?
Meaningful and unique identifiers enhance code readability and comprehension. They make it easier for programmers to understand the purpose and function of different elements within the code.

2. Are Python identifiers case-sensitive?
Yes, Python identifiers are case-sensitive. This means that "variable" and "Variable" are considered as distinct identifiers.

3. What is the scope of an identifier in Python?
The scope of an identifier in Python defines where it can be accessed within the program. Identifiers can have local scope, limited to a specific block of code, or global scope, accessible throughout the entire program.

4. Can Python keywords be used as identifiers?
No, Python keywords, also known as reserved words, cannot be used as identifiers. These words are reserved for specific language constructs and cannot be redefined.

5. Can identifiers begin with a digit in Python?
No, identifiers in Python cannot start with a digit. They must begin with a letter or an underscore.

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