应该不言自明..？:)

# Define a new type for a function-type that accepts an integer and
# a string, returning an integer.
ctypedef int (*f_type)(int, str)

# Extern a function of that type from foo.h
cdef extern from "foo.h":
    int do_this(int, str)

# Passing this function will not work.
cpdef int do_that(int a, str b):
    return 0

# However, this will work.
cdef int do_stuff(int a, str b):
    return 0

# This functio uses a function of that type. Note that it cannot be a
# cpdef function because the function-type is not available from Python.
cdef void foo(f_type f):
    print f(0, "bar")

# Works:
foo(do_this)   # the externed function
foo(do_stuff)  # the cdef function

# Error:
# Cannot assign type 'int (int, str, int __pyx_skip_dispatch)' to 'f_type'
foo(do_that)   # the cpdef function