Use inspect.signature() to inspect functions in Python 3

Give up on `str.endswith` and other non-introspectable things for now.
Adjust docs.

Improves on #108.

README.rst

@@ -92,7 +92,7 @@ And functions:
     all_fn(isa(int), even)      # is_even_int
 
     one_third = rpartial(operator.div, 3.0)
-    has_suffix = rcurry(str.endswith)
+    has_suffix = rcurry(str.endswith, 2)
 
 
 Create decorators easily:

docs/funcs.rst

@@ -65,7 +65,7 @@ Functions
 
     Curries function from last argument to first::
 
-        has_suffix = rcurry(str.endswith)
+        has_suffix = rcurry(str.endswith, 2)
         lfilter(has_suffix("ce"), ["nice", "cold", "ice"])
         # -> ["nice", "ice"]
 

funcy/_inspect.py

@@ -1,5 +1,9 @@
 from __future__ import absolute_import
 from inspect import CO_VARARGS, CO_VARKEYWORDS
+try:
+    from inspect import signature
+except ImportError:
+    signature = None  #
 from collections import namedtuple
 import types
 import re
@@ -105,7 +109,7 @@ def get_spec(func, _cache={}):
     except (KeyError, TypeError):
         pass
 
-    mod = func.__module__
+    mod = getattr(func, '__module__', None)
     if mod in STD_MODULES or mod in ARGS and func.__name__ in ARGS[mod]:
         _spec = ARGS[mod].get(func.__name__, '*')
         required, _, optional = _spec.partition('-')
@@ -144,5 +148,28 @@ def get_spec(func, _cache={}):
             max_n = req_n + 1 if func.__code__.co_flags & CO_VARARGS else n
             return Spec(max_n=max_n, names=names, req_n=req_n, req_names=req_names, kw=kw)
         except AttributeError:
-            raise ValueError('Unable to introspect %s() arguments'
-                                % getattr(func, '__name__', func))
+            # We use signature last to be fully backwards compatible. Also it's slower
+            try:
+                sig = signature(func)
+            except (ValueError, TypeError):
+                raise ValueError('Unable to introspect %s() arguments'
+                    % getattr(func, '__qualname__', None) or getattr(func, '__name__', func))
+            else:
+                spec = _cache[func] = _sig_to_spec(sig)
+                return spec
+
+
+def _sig_to_spec(sig):
+    max_n, names, req_n, req_names, kw = 0, set(), 0, set(), False
+    for name, param in sig.parameters.items():
+        max_n += 1
+        if param.kind == param.VAR_KEYWORD:
+            kw = True
+        elif param.kind == param.VAR_POSITIONAL:
+            req_n += 1
+        else:
+            names.add(name)
+            if param.default is param.empty:
+                req_n += 1
+                req_names.add(name)
+    return Spec(max_n=max_n, names=names, req_n=req_n, req_names=req_names, kw=kw)

tests/test_funcs.py

@@ -28,7 +28,7 @@ class A(object):
 
     assert A().f() == 11
 
-def test_back_partial():
+def test_rpartial():
     assert rpartial(__sub__, 10)(1) == -9
     assert rpartial(pow, 2, 85)(10) == 15
 
@@ -53,6 +53,7 @@ def test_curry_funcy():
 def test_rcurry():
     assert rcurry(__sub__, 2)(10)(1) == -9
     assert rcurry(lambda x,y,z: x+y+z)('a')('b')('c') == 'cba'
+    assert rcurry(str.endswith, 2)('c')('abc') is True
 
 def test_autocurry():
     at = autocurry(lambda a, b, c: (a, b, c))
@@ -97,6 +98,7 @@ def test_autocurry_builtin():
     assert autocurry(complex)(imag=1)(0) == 1j
     assert autocurry(map)(_ + 1)([1, 2]) == [2, 3]
     assert autocurry(int)(base=12)('100') == 144
+    assert autocurry(str.split)(sep='_')('a_1') == ['a', '1']
 
 def test_autocurry_hard():
     def required_star(f, *seqs):