Invalid Variable Name in Python

In Python, variable names are used to store data and refer to specific values. However, there are certain rules and conventions that must be followed when naming variables. One of the options mentioned is not a valid variable name in Python. Let's examine each option and determine which one is not valid.

a) my_variable
b) myVariable
c) 1variable
d) _variable

1. my_variable: Valid Variable Name
The variable name "my_variable" is a valid name in Python. It follows the convention of using lowercase letters and underscores (_) to separate words if needed.

2. myVariable: Valid Variable Name
The variable name "myVariable" is also a valid name in Python. It follows the convention of using lowercase letters for the first word and capitalizing the first letter of each subsequent word (known as CamelCase).

3. 1variable: Invalid Variable Name
The variable name "1variable" is not a valid name in Python. According to Python's naming conventions, variable names cannot start with a number. They can only start with a letter (a-z, A-Z) or an underscore (_).

4. _variable: Valid Variable Name
The variable name "_variable" is a valid name in Python. It follows the convention of using lowercase letters and underscores (_) to separate words if needed. Starting a variable name with an underscore is also allowed.

Conclusion:
The option that is NOT a valid variable name in Python is c) 1variable. Variable names cannot start with a number, so any name starting with a digit will be considered invalid. It is essential to follow the naming conventions and rules to ensure that our code is readable and free of syntax errors.