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flake8-indent-in-def

This is a flake8 plugin enforces 8-space indentation in function/class definitions in Python code.

Installation

pip install flake8-indent-in-def

Violation codes

There is one violation code that this plugin reports:

CodeDescription
IND101hanging indentation in function definition must be 8 spaces
IND102if the 1st argument is on the same line as the function name, all other arguments must be on the same line
IND201hanging indentation in class definition must be 8 spaces
IND202if the 1st base class is on the same line as the class name, all other base classes must be on the same line

Style examples

Wrong

This plugin considers the following indentation styles wrong:

def some_function(arg1,
                  *,
                  arg2,
                  arg3):
    print(arg1)

def some_function(argument1,
                  argument2,
                  argument3, argument4, argumen5):
    print(argument1)

This following style above is the style choice of the black formatter. Both this plugin and PEP8 consider it wrong because arguments and function names would be difficult to visually distinghish.

def some_function(
    arg1: int,
    arg2: list,
    arg3: bool = None,
):
    print(arg1)

Correct

Correspondingly, here are the correct indentation styles:

def some_function(
        arg1: int,
        arg2: list,
        *,
        arg3: bool = None,
):
    print(arg1)

def some_function(
        arg1: int, arg2: list, arg3: bool = None
) -> None:
    print(arg1)

def some_function(arg1: int, arg2: list, arg3: bool = None) -> None:
    print(arg1)

def some_function(
        arg1: int, arg2: list,
        arg3: bool = None, arg4: float = 2.0,
) -> None:
    print(arg1)

Additionally, this plugin by default enforces the same indentation styles on class inheritence:

class MyClass(
        BaseClassA,
        BaseClassB,
        BaseClassC,
):
    def __init__(self):
        pass

You can opt out of class inheritence checks by ignoring rules IND201 and IND202.

Notes

def some_func(
        arg1, arg2, arg3,
        arg4, arg5,
):
    pass

Rationale

When we only indent by 4 spaces in function definitions, it is difficult to visually distinguish function arguments with the function name and the function body. This reduces readability. It is similar for base classes in class definitions, but it's less of an issue than function definitions.

Specifically, the following style is allowed by PEP8 but this plugin still consider it wrong, because it could lead to messy code diff when refactoring:

- def some_very_very_very_long_func(arg1,
+ def some_very_very_very_very_very_long_func(arg1,
                                    arg2,
                                    arg3,

):
    return None

Interaction with other style checkers and formatters