A little demo for typing issue #193.

See python/typing#193 (comment)

Author: Guido van Rossum

misc/variadics.py

@@ -0,0 +1,54 @@
+"""Example of code generation approach to variadics.
+
+See https://github.com/python/typing/issues/193#issuecomment-236383893
+"""
+
+LIMIT = 5
+BOUND = 'object'
+
+def prelude(limit: int, bound: str) -> None:
+    print('from typing import Callable, Iterable, Iterator, Tuple, TypeVar, overload')
+    print('Ts = TypeVar(\'Ts\', bound={bound})'.format(bound=bound))
+    print('R = TypeVar(\'R\')')
+    for i in range(LIMIT):
+        print('T{i} = TypeVar(\'T{i}\', bound={bound})'.format(i=i+1, bound=bound))
+
+def expand_template(template: str,
+                    arg_template: str = 'arg{i}: {Ts}',
+                    lower: int = 0,
+                    limit: int = LIMIT) -> None:
+    print()
+    for i in range(lower, limit):
+        tvs = ', '.join('T{i}'.format(i=j+1) for j in range(i))
+        args = ', '.join(arg_template.format(i=j+1, Ts='T{}'.format(j+1))
+                         for j in range(i))
+        print('@overload')
+        s = template.format(Ts=tvs, argsTs=args)
+        s = s.replace('Tuple[]', 'Tuple[()]')
+        print(s)
+    args_l = [arg_template.format(i=j+1, Ts='Ts') for j in range(limit)]
+    args_l.append('*' + (arg_template.format(i='s', Ts='Ts')))
+    args = ', '.join(args_l)
+    s = template.format(Ts='Ts, ...', argsTs=args)
+    s = s.replace('Callable[[Ts, ...]', 'Callable[...')
+    print('@overload')
+    print(s)
+
+def main():
+    prelude(LIMIT, BOUND)
+
+    # map()
+    expand_template('def map(func: Callable[[{Ts}], R], {argsTs}) -> R: ...',
+                    lower=1)
+    # zip()
+    expand_template('def zip({argsTs}) -> Tuple[{Ts}]: ...')
+
+    # Naomi's examples
+    expand_template('def my_zip({argsTs}) -> Iterator[Tuple[{Ts}]]: ...',
+                    'arg{i}: Iterable[{Ts}]')
+    expand_template('def make_check({argsTs}) -> Callable[[{Ts}], bool]: ...')
+    expand_template('def my_map(f: Callable[[{Ts}], R], {argsTs}) -> Iterator[R]: ...',
+                    'arg{i}: Iterable[{Ts}]')
+                    
+
+main()