feat(method): dict.fromkeys

Author: litlighilit

Objects/dictobjectImpl.nim

@@ -1,13 +1,20 @@
 
 
-import ./pyobject
+
 import ../Python/call
-import ./[stringobject, iterobject, numobjects]
-import ./noneobject
-import ./exceptions
+import ./[
+  pyobject,
+  exceptions, noneobject,
+  stringobject, iterobject,
+  setobject,
+  numobjects,
+  ]
+import ./abstract/[iter, dunder,]
 import ./dictobject
 export dictobject
 from ../Utils/utils import DictError, `!!`
+import ../Python/getargs/vargs
+import ../Include/cpython/critical_section
 
 # redeclare this for these are "private" macros
 
@@ -66,3 +73,50 @@ implDictMagic init:
     pyNone
   else:
     errArgNum argsLen, 1
+
+
+proc fromkeys(mp: PyDictObject, iterable: PyDictObject|PySetObject|PyFrozenSetObject, value: PyObject): PyDictObject =
+  for k in iterable:
+    ## iterable is already a dict, so its keys must be hashable
+    DictError!!(mp[k] = value)
+  mp
+
+proc PyDict_FromKeys*(cls: PyObject, iterable, value: PyObject): PyObject =
+  ## `_PyDict_FromKeys`
+  ## Internal version of dict.from_keys().  It is subclass-friendly
+  let d = call(cls)
+  retIfExc d
+  if d.ofExactPyDictObject:
+    let mp = PyDictObject d
+    template retFor(T) =
+      let it = T iterable
+      criticalWrite mp: criticalRead it:
+        result = mp.fromkeys(it, value)
+      return
+    if iterable.ofExactPyDictObject:
+      retFor PyDictObject
+    elif iterable.ofExactPySetObject:
+      retFor PySetObject
+    elif iterable.ofExactPyFrozenSetObject:
+      let it = PyFrozenSetObject iterable
+      criticalWrite mp: # `criticalRead it:` # frozenset has no lock
+        result = mp.fromkeys(it, value)
+      return
+  let it = PyObject_GetIter(iterable)
+  retIfExc it
+  if d.ofExactPyDictObject:
+    let mp = PyDictObject d
+    criticalWrite mp:
+      pyForIn key, it:
+        retIfExc mp.setItem(key, value)
+  else:
+    pyForIn key, it:
+      retIfExc PyObject_SetItem(d, key, value)
+  d
+
+implDictMethod fromkeys(*a), [classmethod]:
+  var
+    iterable: PyObject
+    value = pyNone
+  PyArg_UnpackTuple("fromkeys", a, 1, 2, iterable, value)
+  PyDict_FromKeys(selfNoCast, iterable, value)