Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://www.geeksforgeeks.org/python-string-isidentifier/ below:

Python String isidentifier() Method - GeeksforGeeks

Last Updated : 04 Jan, 2025

The isidentifier() method in Python is used to check whether a given string qualifies as a valid identifier according to the Python language rules. Identifiers are names used to identify variables, functions, classes, and other objects. A valid identifier must begin with a letter (A-Z or a-z) or an underscore (_), should contain only alphanumeric characters (A-Z, a-z, 0-9) and underscores (_), and should not be a reserved keyword in Python. In this article, we will see how the isidentifier() method works:

Let's understand with the help of an example:

s = "variable_name"
print(s.isidentifier())

Explanation:

• The string "variable_name" follows all the rules of a valid Python identifier:
  • It contains only letters, digits, and underscores.
  • It does not start with a digit.
  • It is not a Python keyword.
• Hence, the method returns True.

string.isidentifier()

• The isidentifier() method does not take any parameters.

• Returns True if the string is a valid identifier.
• Returns False otherwise.

An identifier cannot start with a number.

# Starts with a number
s = "1variable"  

print(s.isidentifier()) 

Explanation:

• The string "1variable" begins with the digit 1, which violates the rules for identifiers.
• Consequently, the method returns False.

Special characters, apart from the underscore, are not allowed in identifiers.

s = "var!name"  # Contains a special character (!)
print(s.isidentifier())  

Explanation:

• The string "var!name" includes the special character !, making it an invalid identifier.
• The method appropriately returns False.

Python’s reserved keywords cannot be used as identifiers. While they follow the naming rules, their special meaning in the language makes them invalid as identifiers:

s = "class"  # Reserved keyword in Python
print(s.isidentifier()) 

Explanation:

• The string "class" follows all identifier rules, so isidentifier() returns True.
• However, using it as an identifier in code will lead to a SyntaxError because it is a reserved keyword.

An empty string cannot qualify as an identifier:

s = ""  # Empty string
print(s.isidentifier())  

Explanation:

• The string is empty, so it cannot meet the rules for identifiers.
• The method returns False accordingly.

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4