How to use Cython - 10 common examples

@cython.locals(d=dict)
def setdefault2(d, key, value):
    """
    >>> d = {}
    >>> setdefault2(d, 1, 2)
    2
    >>> len(d)
    1
    >>> setdefault2(d, 1, 2)
    2
    >>> len(d)
    1
    >>> l = setdefault2(d, 2, [])
    >>> len(d)
    2
    >>> l.append(1)
    >>> setdefault2(d, 2, [])

@cython.locals(x=X)
def x_of(x):
    return x.x

# mode: run
# tag: annotation_typing, pure3.0

import cython

is_compiled = cython.compiled

MyUnion = cython.union(n=cython.int, x=cython.double)
MyStruct = cython.struct(is_integral=cython.bint, data=MyUnion)
MyStruct2 = cython.typedef(MyStruct[2])


@cython.ccall  # cpdef => C return type
def test_return_type(n: cython.int) -> cython.double:
    """
    >>> test_return_type(389)
    389.0
    """
    assert cython.typeof(n) == 'int', cython.typeof(n)
    return n if is_compiled else float(n)

def test_method():
    """
    >>> test_method()
    4
    True
    """
    x = PureFoo(2)
    print(x.puremeth(2))
    if cython.compiled:
        print(isinstance(x(), float))
    else:
        print(True)
    return

def test_imports():
    """
    >>> test_imports()
    (True, True)
    """
    a = cython.NULL
    b = declare(p_void, cython.NULL)
    c = my_declare(my_void_star, cython.NULL)
    d = cy.declare(cy.p_void, cython.NULL)

    return a == d, compiled == my_compiled

def test_sizeof():
    """
    >>> test_sizeof()
    True
    True
    True
    True
    True
    """
    x = cython.declare(cython.bint)
    print(cython.sizeof(x) == cython.sizeof(cython.bint))
    print(sizeof(cython.char) <= sizeof(cython.short) <= sizeof(cython.int) <= sizeof(cython.long) <= sizeof(cython.longlong))
    print(cython.sizeof(cython.uint) == cython.sizeof(cython.int))
    print(cython.sizeof(cython.p_int) == cython.sizeof(cython.p_double))
    if cython.compiled:
        print(cython.sizeof(cython.char) < cython.sizeof(cython.longlong))
    else:
        print(cython.sizeof(cython.char) == 1)

@cython.locals(x=cython.int)
@cython.returns(cython.int)
def cdef_nogil_true(x):
    return x + 1

@cython.returns(cython.int)
def cdef_nogil_true(x):
    return x + 1

@cython.locals(x=cython.int, y=cython.p_int)
def test_address(x):
    """
    >>> test_address(39)
    39
    """
    y = cython.address(x)
    return y[0]

# mode: run
# tag: pure3.6, pep526, pep484, warnings

import cython

from typing import Dict, List, TypeVar, Optional, Generic, Tuple
try:
    from typing import ClassVar
except ImportError:
    ClassVar = Optional  # fake it in Py3.5


var = 1  # type: annotation
var: int = 2
fvar: float = 1.2
some_number: cython.int    # variable without initial value
some_list: List[int] = []  # variable with initial value
t: Tuple[int, ...] = (1, 2, 3)
body: Optional[List[str]]
descr_only : "descriptions are allowed but ignored"


some_number = 5
body = None


def f():
    """
    >>> f()
    (2, 1.5, [], (1, 2, 3))
    """
    var = 1  # type: annotation