bespon 0.1.1

Python library for BespON

The bespon package for Python encodes and decodes data in the BespON format.

Basic usage

Data is loaded in a manner analogous to the json package:

• bespon.load(<file-like object>)

• bespon.loads(<string or bytes>)

Similarly, dumping data to a file or string:

• bespon.dump(<obj>, <file-like object>)

• bespon.dumps(<obj>)

At the moment, only dumping in indentation-style syntax is possible. Support for other styles may be added in the future. Only dicts, lists, Unicode strings, floats, ints, bools, and None are currently supported for dumping.

Lossless round-trip support

There is also support for lossless round-tripping. Data can be loaded, values can be modified, and then data can be saved again with minimal impact on the data file layout.

Data can be loaded from a file or string into an instance of the RoundtripAst class.

• bespon.load_roundtrip_ast(<file-like object>)

• bespon.loads_roundtrip_ast(<string or bytes>)

This class has two methods that allow data to be modified.

• replace_val(<path>, <obj>) This replaces the object currently located at <path> within the data with <obj>. <path> must be a list or tuple consisting of dict keys and list indices. <obj> must currently be a Unicode string, float, int, or bool, and must have the same type as the object it is replacing.

• replace_key(<path>, <obj>) This replaces the dict key at the end of <path> with the new key <obj> (which will map to the same value as the replaced key). <obj> must be a Unicode string, int, or bool, and must have the same type as the object it is replacing.

After data in a RoundtripAst instance has been modified, it may be encoded back into a string with the dumps() method. An example is shown below.

>>> ast = bespon.loads_roundtrip_ast("""
key.subkey.first = 123   # Comment
key.subkey.second = 0b1101
key.subkey.third = `literal \string`
""")
>>> ast.replace_key(['key', 'subkey'], 'sk')
>>> ast.replace_val(['key', 'sk', 'second'], 7)
>>> ast.replace_val(['key', 'sk', 'third'], '\\another \\literal')
>>> ast.replace_key(['key', 'sk', 'third'], 'fourth')
>>> print(ast.dumps())

key.sk.first = 123   # Comment
key.sk.second = 0b111
key.sk.fourth = `\another \literal`

This example illustrates several of BespON’s round-trip capabilities.

• Comments and layout are preserved exactly.

• Key renaming works with key paths. Every time a key appears in key paths, it is renamed.

• When a number is modified, the new value is expressed in the same base as the old value.

• When a quoted string is modified, the new value is quoted in the same style as the old value (at least to the extent that this is practical).

• As soon as a key is modified, the new key must be used for further modifications. The old key is invalid.

Currently, round-trip support is limited to changing the value of any Unicode string, float, int, or bool, without changing the type. Support for changing data types and for more general data manipulation will be added in the future.

Spec conformance

The bespon package passes the BespON test suite.