ASP

This package implements a custom parser for BUILD files.

Asp is syntactically a subset of Python, with many of its more advanced or dynamic features stripped out. Some of the notable differences are:

• The import, try, except, finally, class, global, nonlocal, while and async keywords are not available. These are also prohibited from being used as identifiers in order to maintain compatibility.
• The assert statement is supported, but it is not possible to catch any resulting error (since try and except don't exist).
• List and dict comprehensions are supported, but not Python's more general generator expressions. Up to two 'for' clauses are permitted.
• Most builtin functions are not available.
• Dictionaries are supported, but can only be keyed by strings. They always iterate in a consistent order.
• The only builtin types are bool, int, str, list, dict and functions. There are no float, complex, set, frozenset or bytes types.
• Operators +, <, >, %, and, or, in, not in, is, is not, ==, >=, <= and != are supported in most appropriate cases. Other operators are not available.
• String interpolation is available via % and f-strings. format() is also available but its implementation is incomplete and use is discouraged.
• The += augmented assignment operator is available in addition to = for normal assignment. Other augmented assignment operations aren't available.
• Function arguments are evaluated at call time rather than at parse time; hence it is safe to use mutable defaults such as a list or dict.
• Type annotations are available and are checked at runtime. Options can be combined with the | operator (e.g. foo:list|dict=[]).
• append and extend on list objects are troublesome - our lists are a little more immutable (80% of the time they're immutable every time) than Python lists and hence those functions sort of work but don't have exactly the same semantics as the original (e.g. they may not always modify the original if it originated from a surrounding scope). Users are encouraged to use the += augmented assignment operator instead.

The name is reminiscent of AST, and a play on an asp being a smaller snake than a python.