Python Variables

Python Variables: Assignment, Naming Rules, and Unpacking

A Python variable is a named label attached to an object in memory, created the moment you assign a value with =. You never need to declare a variable type in advance because Python tracks the type on the value itself.

Because variables hold references rather than fixed boxes, you can rebind a name to a new value at any time. Keeping variable types consistent inside a function still makes your code far easier to debug.

Creating and Unpacking Variables

You can assign single values, chain one value to multiple names, or unpack a sequence into separate variables on one line.

# Standard assignment
customer_id = 4082
account_active = True

# Tuple unpacking
width, height = 1920, 1080
first_name, last_name = "Nadia", "Karim"

print(customer_id, width, height, first_name)

Unpacking swaps two variables without a temporary variable: a, b = b, a.

Variable Naming Rules and Conventions

Python enforces strict syntax rules for identifier names and adds community style standards in PEP 8:

• Start names with a letter (a-z, A-Z) or underscore _, never a digit.
• Use only letters, numbers, and underscores (user_age, item2).
• Avoid Python reserved keywords such as class, for, return, or import.
• Use snake_case for variables and UPPER_SNAKE_CASE for module-level constants like MAX_UPLOAD_MB = 25.

Common Mistakes to Avoid

• Shadowing built-in functions: Naming a variable list, str, id, or sum overrides Python's built-in name in that scope.
• Misunderstanding shared mutable references: Writing b = a on a list points both names to the same list, so mutating b changes a too.
• Reusing one variable name for unrelated types: Switching data from a raw string to a dictionary mid-function often hides bugs.

Frequently Asked Questions

How do I check a variable's type in Python?

Pass the variable to the built-in type() function, such as type(customer_id), which prints <class 'int'>.

Are Python variables case-sensitive?

Yes. userScore and userscore refer to completely different variables in Python.

How do I delete a variable in Python?

Use the del statement (del temp_cache) to remove the name binding from the current namespace.