Hello, On Fri, 12 Feb 2021 18:26:53 +1100 Chris Angelico <ros...@gmail.com> wrote:
> On Fri, Feb 12, 2021 Paul Sokolovsky <pmis...@gmail.com> wrote: > > ... And on the 2nd thought, that won't work. The reason it works in > > JS is that it doesn't have tuples. In Python, "(a, b) => (1, 2)" > > means "compare a tuple for greater-or-equal". > > Should be safe actually - "=>" is not a valid comparison operator. To punish myself for making such stupid mistakes, I volunteered to implement PoC of that. And by long honorable tradition, improvements to Python get implemented in Python first. So with my "imphook" thingy https://pypi.org/project/imphook/, and with the hook module at the end, following works as expected: =========== $ cat example_arrow_func.py f = (a, b) => a + b print(f(1, 2)) res = ((a, b) => a + b)(3, 4) print(res) print(list(map((x) => x * 2, [1, 2, 3, 4]))) # Confirm there's no crashing on bare tuple at the tail of file. (1, 2) $ python3 -m imphook -i mod_arrow_func -m example_arrow_func 3 7 [2, 4, 6, 8] =========== The implementation was written a bit cowboyishly in 15 mins, maybe, just maybe, you can still crash it. (For example, it clearly doesn't support newlines in arrow param list): ===== mod_arrow_func.py ====== import sys import tokenize import imphook class TokBuf: def __init__(self): self.tokens = [] def append(self, t): self.tokens.append(t) def clear(self): self.tokens.clear() def empty(self): return not self.tokens def spool(self): yield from self.tokens self.clear() def xform(token_stream): tokbuf = TokBuf() for t in token_stream: if t[1] == "(": # We're interested only in the deepest parens. if not tokbuf.empty(): yield from tokbuf.spool() tokbuf.append(t) elif t[1] == ")": nt1 = next(token_stream) nt2 = next(token_stream) if nt1[1] == "=" and nt2[1] == ">": yield (tokenize.NAME, "lambda") yield from tokbuf.tokens[1:] tokbuf.clear() yield (tokenize.OP, ":") else: yield from tokbuf.tokens tokbuf.clear() yield t yield nt1 yield nt2 elif not tokbuf.empty(): tokbuf.append(t) else: yield t def hook(modname, filename): with open(filename, "rb") as f: # Fairly speaking, tokenizing just to convert back to string form # isn't too efficient, but CPython doesn't offer us a way to parse # token stream so far, so we have no choice. source = tokenize.untokenize(xform(tokenize.tokenize(f.readline))) mod = type(imphook)(modname) exec(source, vars(mod)) return mod imphook.add_import_hook(hook, (".py",)) =========== -- Best regards, Paul mailto:pmis...@gmail.com _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/VOVHZUNJKCVCIPPMA4EBUJ2CQ5FJJR2F/ Code of Conduct: http://python.org/psf/codeofconduct/
