Valid Python Identifier

Given a string, determine whether it is a valid Python identifier.

A valid Python identifier must satisfy the following conditions:

• The string is non-empty.
• The first character is either a letter (a-z or A-Z) or an underscore ('_').
• Each subsequent character is either a letter, a digit, or an underscore.

This can be expressed mathematically using LaTeX as follows:

$$ s \neq \epsilon, \quad s[0] \in [a-zA-Z\_] \quad \text{and} \quad \forall i \geq 1,\, s[i] \in [a-zA-Z0-9\_] $$

Write a program that reads an input string and outputs True if it is a valid Python identifier, otherwise outputs False.

inputFormat

The input consists of a single line containing the string to be checked. Any leading or trailing whitespace should be ignored.

outputFormat

Output a single line: True if the input string is a valid Python identifier, and False otherwise.

variable

True