self as First Argument

ID

python.self_first_argument

Severity

low

Remediation Complexity

trivial

Remediation Risk

medium

Remediation Effort

low

Resource

Naming Convention

Language

Python

Tags

code-style, naming

Description

Reports instance methods whose first parameter is not named self. Python uses the first parameter as the "this" reference of the method, and PEP 8 establishes the convention self. A method named def foo(this, x) works at runtime, but every reader pays a moment of confusion to verify that nothing else broke.

class Bad:
    def foo(this):       # FLAW
        return this

class Good:
    def foo(self):
        return self

    @staticmethod
    def helper(x):       # OK — static, no implicit first arg
        return x

Rationale

Convention is the whole point: a name that breaks the convention demands the reader’s attention every time, even when nothing else is wrong. self is also what every editor / tooling / docstring template assumes.

Remediation

Rename the parameter to self. The rest of the method body needs the same rename in lockstep, but every IDE handles that automatically.

References