numpy.core._dtype_ctypes

module documentation

Conversion from ctypes to dtype.

In an ideal world, we could achieve this through the PEP3118 buffer protocol, something like:

def dtype_from_ctypes_type(t):
    # needed to ensure that the shape of `t` is within memoryview.format
    class DummyStruct(ctypes.Structure):
        _fields_ = [('a', t)]

    # empty to avoid memory allocation
    ctype_0 = (DummyStruct * 0)()
    mv = memoryview(ctype_0)

    # convert the struct, and slice back out the field
    return _dtype_from_pep3118(mv.format)['a']

Unfortunately, this fails because:

  • ctypes cannot handle length-0 arrays with PEP3118 (bpo-32782)
  • PEP3118 cannot represent unions, but both numpy and ctypes can
  • ctypes cannot handle big-endian structs with PEP3118 (bpo-32780)
Function ​_from​_ctypes​_array Undocumented
Function ​_from​_ctypes​_scalar Return the dtype type with endianness included if it's the case
Function ​_from​_ctypes​_structure Undocumented
Function ​_from​_ctypes​_union Undocumented
Function dtype​_from​_ctypes​_type Construct a dtype object from a ctypes type
def _from_ctypes_array(t):

Undocumented

def _from_ctypes_scalar(t):
Return the dtype type with endianness included if it's the case
def _from_ctypes_structure(t):

Undocumented

def _from_ctypes_union(t):

Undocumented

def dtype_from_ctypes_type(t):
Construct a dtype object from a ctypes type