perky

A friendly, easy, Pythonic text file format

Copyright 2018-2019 by Larry Hastings

Overview

Perky is a new, simple "rcfile" text file format for Python programs.

The following are Perky features:

Perky syntax

Perky configuration files look something like JSON without the quoting.

example name = value
example dict = {
    name = 3
    another name = 5.0
    }
example list = [
    a
    b
    c
    ]
# lines starting with hash are ignored

# blank lines are ignored

" quoted name " = " quoted value "

triple quoted string = """

    indenting
        is preserved

    the string is automatically outdented
    to the leftmost character of the ending
    triple-quote

    <-- aka here
    """

Explicit transformation is better than implicit

One possibly-surprising design choice of Perky: the only natively supported values for the Perky parser are dicts, lists, and strings. Other commonly-used types (ints, floats, etc) are handled using a different mechanism: transformation.

A Perky transformation takes a dict as input, and transforms the contents of the dict based on a schema. A Perky schema is a dict with the same general shape as the dict produced by the Perky parse, but it contains dicts, lists, and transformation functions. If you want myvalue in {'myvalue':'3'} to be a real integer, transform it with the schema {'myvalue': int}.

API

perky.loads(s) -> d

Parses a string containing Perky-file-format settings. Returns a dict.

perky.load(filename, encoding="utf-8") -> d

Parses a file containing Perky-file-format settings. Returns a dict.

perky.dumps(d) -> s

Converts a dictionary to a Perky-file-format string. Keys in the dictionary must all be strings. Values that are not dicts, lists, or strings will be converted to strings using str. Returns a string.

perky.dump(filename, d, encoding="utf-8")

Converts a dictionary to a Perky-file-format string using perky.dump, then writes it to filename.

perky.map(d, fn) -> o

Iterates over a dictionary. Returns a new dictionary where, for every value:

• if it is a dict, replace with a new dict.
• if it is a list, replace with a new list.
• if it is neither a dict nor a list, replace with fn(value).

The function passed in is called a conversion function.

perky.transform(d, schema, default=None) -> o

Recursively transforms a Perky dict into some other object (usually a dict) using the provided schema. Returns a new dict.

A schema is a data structure matching the general expected shape of d, where the values are dicts, lists, and callables. The transformation is similar to perky.map() except that individual values will have individual conversion functions. Also, a schema conversion function can be specified for any value in d, even dicts or lists.

default is a default conversion function. If there is a value v in d that doesn't have an equivalent entry in schema, and v is neither a list nor a dict, and if default is a callable, v will be replaced with default(v) in the output.

perky.Required

Experimental.

perky.nullable(fn) -> fn

Experimental.

perky.const(fn) -> o

Experimental.

TODO

• Backslash quoting currently does "whatever your version of Python does". Perhaps this should be explicit, and parsed by Perky itself?