advanced syntax&semantics extension system for Python
Project description
Moshmosh
An advanced syntax extension system implemented in pure python.
pip install moshmosh-base
Preview
Working with IPython
You should copy moshmosh_ipy.py
to $USER/.ipython/profile_default/startup/
.
If this directory does not exist, use command ipython profile create
to instantiate.
Some examples about pattern matching, pipelines and quick lambdas:
Some examples about the scoped operators:
Working with regular Python files
Import moshmosh
in your main module:
Then, in mypackage.py
, start coding with a pragma comment # moshmosh?
, then you can use moshmosh extension system.
Case Study : Pattern Matching
The matching protocol which stems from Python-ideas mailing list is introduced in, which means you can define your own patterns conveniently. The link is here.
# moshmosh?
# +pattern-matching
class GreaterThan:
def __init__(self, v):
self.v = v
def __match__(self, cnt: int, to_match):
if isinstance(to_match, int) and cnt is 0 and to_match > self.v:
return () # matched
# 'return None' indicates 'unmatched'
with match(114, 514):
if (GreaterThan(42)() and a, b):
print(b, a)
# 514 114
Note that the matching clauses should be exhaustive,
otherwise, a moshmosh.extensions.pattern_matching.runtime.NotExhaustive
might get raised.
The supported Patterns are listed here, which is of course much more powerful than most programming languages.
- And pattern:
pat1 and pat2 and pat3 ...
- Or pattern:
pat1 or pat2 or pat3...
- Pin pattern:
pin(value)
, this is quite useful. See Elixir Pin Operator - Literal pattern:
1, "str", 1+2j, (1, 2)
- As pattern:
a, var
- Wildcard:
_
- Nested patterns:
- Tuple:
(pat1, pat2, pat3), (pat1, *pat2, pat3)
- List:
[pat1, pat2, pat3], [pat1, *pat2, pat3]
- Recogniser:
Cons(pat1, pat2, pat3)
, note that, the functionCons.__match__(<n arg>, value_to_match)
is exact the protocol.
- Tuple:
The pattern matching should be more efficient than those hand-written codes without ugly optimizations.
Besides, Moshmosh's pattern matching is orders of magnitude faster than any other alternatives.
Case Study : Template-Python
This is relatively a simple quasiquote implementation, inspired by MetaOCaml. It does not support manual splices or nested quotations, but the function arguments are automatically spliced.
# moshmosh?
# +template-python
@quote
def f(x):
x + 1
x = y + 1
from moshmosh.ast_compat import ast
from astpretty import pprint
stmts = f(ast.Name("a"))
pprint(ast.fix_missing_locations(stmts[0]))
pprint(ast.fix_missing_locations(stmts[1]))
# =>
Expr(
lineno=7,
col_offset=4,
value=BinOp(
lineno=7,
col_offset=4,
left=Name(lineno=7, col_offset=4, id='a', ctx=Load()),
op=Add(),
right=Num(lineno=7, col_offset=8, n=1),
),
)
Assign(
lineno=8,
col_offset=4,
targets=[Name(lineno=8, col_offset=4, id='a', ctx=Store())],
value=BinOp(
lineno=8,
col_offset=8,
left=Name(lineno=8, col_offset=8, id='y', ctx=Load()),
op=Add(),
right=Num(lineno=8, col_offset=12, n=1),
),
)
Acknowledgements
- future-fstrings
- Pattern matching in Python
- older implementations
- search "pattern matching" at Python-ideas.
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