m-o

A command line tool for parsing Python dataclass reprs and pretty-printing them. The name is based on the WALL-E character M-O, a robot who liked to clean things up.

Example

# my_data.py

@dataclass
class Dog:
    name: str
    age: int
    friends: List[str]

pip = Dog("Pip", 7, ["Quincy", "Digger"])
print(pip)

$ # without m-o:
$ python my_data.py
Dog(name="Pip", age=7, friends=["Quincy", "Digger"])

$ # with m-o:
$ python my_data.py | m-o
Dog(
    name="Pip",
    age=7,
    friends=[
        "Quincy",
        "Digger",
    ],
)

why tho?

Python's pprint.pprint function allows common values (tuples, lists, dicts, etc.) to be pretty-printed, but does not know how to format Python 3.7's dataclasses. I use dataclasses pretty frequently, and often need to debug deeply nested trees of dataclasses. The __repr__ method on dataclasses displays everything on one line which is difficult to read.

Rather than implementing pprint.pprint for your dataclasses (who even knows how to do this anyway?), just print out the value and pipe it into this tool. The data structure will be pretty-printed to your terminal.

Installation

$ cargo install m-o

(Planned/Current) Features

[x] Parse string escape characters (0.1.5) [ ] Use "Wadler-style" pretty-printing algorithm