tinysexpr 1.3

A very simple S-expression parser that tries to make as little fuss as possible.

S-Expression Parser

A very simple S-expression parser that tries to make as little fuss as possible.

Example

This module provides a single function

def read(file_like, delims=DEFAULT_DELIMS, comment_char=';', atom_handler=lambda x: x):

that returns the read S-expression. Reading

(a b c (123 e f () x))

returns

['a', 'b', 'c', ['123', 'e', 'f', [], 'x']]

Atoms

a, b, c in the above example are called atoms. Atoms are parsed using two different rules:

1. Every sequence that does not contain a whitespace, opening of closing parenthesis or the comment character is an atom.
2. Every sequence that starts and ends with a delimiter is an atom. The default delimiters are " for strings with the usual escape characters (\n, \t, \", \\, ...) and | without escape characters. Using the delims parameter, you can customize the delimiters and their escape sequences.

Details

The parameters of read are:

1. file_like: An object that is file like i.e. provides a read method.
2. delims: A map of delimiters used to surround atoms that contain spaces. Commonly these are double-quotes to represent strings as in "Hello" or vertical bars to allow for symbols that contain spaces as in |some symbol|. The map DEFAULT_DELIMS specifies delimiters for strings and symbols.
3. comment_char: The character that starts a single line comment. The default value is ;.
4. atom_handler: A function that is called when an atom is parsed. This function is passed a string that consists of the text of the parsed atom. The function can convert this string into something else and the returned value is used to construct the S-expression. For example, this allows for converting digit sequences into ints.

Testing

To run the tests, execute python -m pytest.