S-expression parser for Python

sexpdata is a simple S-expression parser/serializer. It has simple load and dump functions like pickle, json or PyYAML module.

>>> from sexpdata import loads, dumps
>>> loads('("a" "b")')
['a', 'b']
>>> print(dumps(['a', 'b']))
("a" "b")

You can install sexpdata from PyPI:

pip install sexpdata

Links:

• Documentation (at Read the Docs)
• Repository (at GitHub)
• Issue tracker (at GitHub)
• PyPI
• Travis CI

License

sexpdata is licensed under the terms of the BSD 2-Clause License. See the source code for more information.

sexpdata.load(filelike, **kwds)

Load object from S-expression stored in filelike.

Parameters:filelike – A text stream object.

See loads() for valid keyword arguments.

>>> import io
>>> fp = io.StringIO()
>>> sexp = [Symbol('a'), Symbol('b')]   # let's dump and load this object
>>> dump(sexp, fp)
>>> _ = fp.seek(0)
>>> load(fp) == sexp
True

sexpdata.loads(string, **kwds)

Load object from S-expression string.

Parameters:

• string – String containing an S-expression.
• nil (str or None) – A symbol interpreted as an empty list. Default is 'nil'.
• true (str or None) – A symbol interpreted as True. Default is 't'.
• false (str or None) – A symbol interpreted as False. Default is None.
• line_comment (str) – Beginning of line comment. Default is ';'.

>>> loads("(a b)")
[Symbol('a'), Symbol('b')]
>>> loads("a")
Symbol('a')
>>> loads("(a 'b)")
[Symbol('a'), Quoted(Symbol('b'))]
>>> loads("(a '(b))")
[Symbol('a'), Quoted([Symbol('b')])]
>>> loads('''
... ;; This is a line comment.
... ("a" "b")  ; this is also a comment.
... ''')
['a', 'b']
>>> loads('''
... # This is a line comment.
... ("a" "b")  # this is also a comment.
... ''', line_comment='#')
['a', 'b']

nil is converted to an empty list by default. You can use keyword argument nil to change what symbol must be interpreted as nil:

>>> loads("nil")
[]
>>> loads("null", nil='null')
[]
>>> loads("nil", nil=None)
Symbol('nil')

t is converted to True by default. You can use keyword argument true to change what symbol must be converted to True.:

>>> loads("t")
True
>>> loads("#t", true='#t')
True
>>> loads("t", true=None)
Symbol('t')

No symbol is converted to False by default. You can use keyword argument false to convert a symbol to False.

>>> loads("#f")
Symbol('#f')
>>> loads("#f", false='#f')
False
>>> loads("nil", false='nil', nil=None)
False

sexpdata.dump(obj, filelike, **kwds)

Write obj as an S-expression into given stream filelike.

Parameters:

• obj – A Python object.
• filelike – A text stream object.

See dumps() for valid keyword arguments.

>>> import io
>>> fp = io.StringIO()
>>> dump([Symbol('a'), Symbol('b')], fp)
>>> print(fp.getvalue())
(a b)

sexpdata.dumps(obj, **kwds)

Convert python object into an S-expression.

Parameters:

• obj – A Python object.
• str_as ('symbol' or 'string') – How string should be interpreted. Default is 'string'.
• tuple_as ('list' or 'array') – How tuple should be interpreted. Default is 'list'.
• true_as (str) – How True should be interpreted. Default is 't'
• false_as (str) – How False should be interpreted. Default is '()'
• none_as (str) – How None should be interpreted. Default is '()'

Basic usage:

>>> print(dumps(['a', 'b']))
("a" "b")
>>> print(dumps(['a', 'b'], str_as='symbol'))
(a b)
>>> print(dumps(dict(a=1, b=2)))
(:a 1 :b 2)
>>> print(dumps([None, True, False, ()]))
(() t () ())
>>> print(dumps([None, True, False, ()],
...             none_as='null', true_as='#t', false_as='#f'))
(null #t #f ())
>>> print(dumps(('a', 'b')))
("a" "b")
>>> print(dumps(('a', 'b'), tuple_as='array'))
["a" "b"]

More verbose usage:

>>> print(dumps([Symbol('a'), Symbol('b')]))
(a b)
>>> print(dumps(Symbol('a')))
a
>>> print(dumps([Symbol('a'), Quoted(Symbol('b'))]))
(a 'b)
>>> print(dumps([Symbol('a'), Quoted([Symbol('b')])]))
(a '(b))

sexpdata.car(obj)

Alias of obj[0].

>>> car(loads('(a . b)'))
Symbol('a')
>>> car(loads('(a b)'))
Symbol('a')

sexpdata.cdr(obj)

cdr-like function.

>>> cdr(loads('(a . b)'))
Symbol('b')
>>> cdr(loads('(a b)'))
[Symbol('b')]
>>> cdr(loads('(a . (b))'))
[Symbol('b')]
>>> cdr(loads('(a)'))
[]
>>> cdr(loads('(a . nil)'))
[]

Changelog

v0.0.3

• Encoded raw string can be dumped to S-expression, assuming that the encoding is UTF-8. See also tkf/emacs-jedi/#43.

v0.0.2

• Performance improvement. Especially for long string literal.

v0.0.1

• Initial release.

Indices and tables

• Index
• Module Index
• Search Page