Cython與numpy ctypedef：什麼是正確的約定？

Question

在用Cython使用numpy的時候，什麼是寫作的一點：

cimport numpy as np 
import numpy as np 
ctypedef np.int_t DTYPE_t 

，然後使用DTYPE_t隨處可見，而不是僅僅使用np.int_t？ ctypedef實際上在結果代碼中做了什麼不同的事情嗎？

Answer 1

您可以從docs for cython閱讀筆記，讀他們解釋了使用這種符號和進口的原因說明。

from __future__ import division 
import numpy as np 
# "cimport" is used to import special compile-time information 
# about the numpy module (this is stored in a file numpy.pxd which is 
# currently part of the Cython distribution). 
cimport numpy as np 
# We now need to fix a datatype for our arrays. I've used the variable 
# DTYPE for this, which is assigned to the usual NumPy runtime 
# type info object. 
DTYPE = np.int 
# "ctypedef" assigns a corresponding compile-time type to DTYPE_t. For 
# every type in the numpy module there's a corresponding compile-time 
# type with a _t-suffix. 
ctypedef np.int_t DTYPE_t 
# "def" can type its arguments but not have a return type. The type of the 
# arguments for a "def" function is checked at run-time when entering the 
# function. 
# 
# The arrays f, g and h is typed as "np.ndarray" instances. The only effect 
# this has is to a) insert checks that the function arguments really are 
# NumPy arrays, and b) make some attribute access like f.shape[0] much 
# more efficient. (In this example this doesn't matter though.)