Issue #19611: handle implicit parameters in inspect.signature
inspect.signature now reports the implicit ``.0`` parameters generated by
the compiler for comprehension and generator expression scopes as if they
were positional-only parameters called ``implicit0``.
Patch by Jelle Zijlstra.
diff --git a/Doc/library/inspect.rst b/Doc/library/inspect.rst
index 3994850..3b36379 100644
--- a/Doc/library/inspect.rst
+++ b/Doc/library/inspect.rst
@@ -625,6 +625,16 @@
The name of the parameter as a string. The name must be a valid
Python identifier.
+ .. impl-detail::
+
+ CPython generates implicit parameter names of the form ``.0`` on the
+ code objects used to implement comprehensions and generator
+ expressions.
+
+ .. versionchanged:: 3.6
+ These parameter names are exposed by this module as names like
+ ``implicit0``.
+
.. attribute:: Parameter.default
The default value for the parameter. If the parameter has no default
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 582bb0e..45d2110 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -2396,6 +2396,20 @@
if not isinstance(name, str):
raise TypeError("name must be a str, not a {!r}".format(name))
+ if name[0] == '.' and name[1:].isdigit():
+ # These are implicit arguments generated by comprehensions. In
+ # order to provide a friendlier interface to users, we recast
+ # their name as "implicitN" and treat them as positional-only.
+ # See issue 19611.
+ if kind != _POSITIONAL_OR_KEYWORD:
+ raise ValueError(
+ 'implicit arguments must be passed in as {}'.format(
+ _POSITIONAL_OR_KEYWORD
+ )
+ )
+ self._kind = _POSITIONAL_ONLY
+ name = 'implicit{}'.format(name[1:])
+
if not name.isidentifier():
raise ValueError('{!r} is not a valid parameter name'.format(name))
diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index 76cebcc..47244ae 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -2903,6 +2903,10 @@
'is not a valid parameter name'):
inspect.Parameter('$', kind=inspect.Parameter.VAR_KEYWORD)
+ with self.assertRaisesRegex(ValueError,
+ 'is not a valid parameter name'):
+ inspect.Parameter('.a', kind=inspect.Parameter.VAR_KEYWORD)
+
with self.assertRaisesRegex(ValueError, 'cannot have default values'):
inspect.Parameter('a', default=42,
kind=inspect.Parameter.VAR_KEYWORD)
@@ -2986,6 +2990,17 @@
with self.assertRaisesRegex(TypeError, 'name must be a str'):
inspect.Parameter(None, kind=inspect.Parameter.POSITIONAL_ONLY)
+ @cpython_only
+ def test_signature_parameter_implicit(self):
+ with self.assertRaisesRegex(ValueError,
+ 'implicit arguments must be passed in as'):
+ inspect.Parameter('.0', kind=inspect.Parameter.POSITIONAL_ONLY)
+
+ param = inspect.Parameter(
+ '.0', kind=inspect.Parameter.POSITIONAL_OR_KEYWORD)
+ self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_ONLY)
+ self.assertEqual(param.name, 'implicit0')
+
def test_signature_parameter_immutability(self):
p = inspect.Parameter('spam', kind=inspect.Parameter.KEYWORD_ONLY)
@@ -3234,6 +3249,17 @@
ba = sig.bind(args=1)
self.assertEqual(ba.arguments, {'kwargs': {'args': 1}})
+ @cpython_only
+ def test_signature_bind_implicit_arg(self):
+ # Issue #19611: getcallargs should work with set comprehensions
+ def make_set():
+ return {z * z for z in range(5)}
+ setcomp_code = make_set.__code__.co_consts[1]
+ setcomp_func = types.FunctionType(setcomp_code, {})
+
+ iterator = iter(range(5))
+ self.assertEqual(self.call(setcomp_func, iterator), {0, 1, 4, 9, 16})
+
class TestBoundArguments(unittest.TestCase):
def test_signature_bound_arguments_unhashable(self):
diff --git a/Misc/ACKS b/Misc/ACKS
index ee67e27..7f289fb 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1665,6 +1665,7 @@
Cheng Zhang
Kai Zhu
Tarek Ziadé
+Jelle Zijlstra
Gennadiy Zlobin
Doug Zongker
Peter Åstrand
diff --git a/Misc/NEWS b/Misc/NEWS
index 5a1d4d5..0dc317e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -27,6 +27,11 @@
Library
-------
+- Issue #19611: :mod:`inspect` now reports the implicit ``.0`` parameters
+ generated by the compiler for comprehension and generator expression scopes
+ as if they were positional-only parameters called ``implicit0``.
+ Patch by Jelle Zijlstra.
+
- Issue #26809: Add ``__all__`` to :mod:`string`. Patch by Emanuel Barry.
- Issue #26373: subprocess.Popen.communicate now correctly ignores