c下劃線表達式`c_`做了什麼？

Question

它似乎是某種水平連接，但我在網上找不到任何文檔。這裏最小的工作例如：

In [1]: from numpy import c_ 
In [2]: a = ones(4) 
In [3]: b = zeros((4,10))  
In [4]: c_[a,b] 
Out[4]: 
array([[ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], 
     [ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], 
     [ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.], 
     [ 1., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]]) 

Answer 1

使用IPython中的?語法來獲得更多的信息：

In [2]: c_? 
Type:  CClass 
Base Class: <class 'numpy.lib.index_tricks.CClass'> 
String Form:<numpy.lib.index_tricks.CClass object at 0x9a848cc> 
Namespace: Interactive 
Length:  0 
File:  /usr/lib/python2.7/dist-packages/numpy/lib/index_tricks.py 
Docstring: 
Translates slice objects to concatenation along the second axis. 

This is short-hand for ``np.r_['-1,2,0', index expression]``, which is 
useful because of its common occurrence. In particular, arrays will be 
stacked along their last axis after being upgraded to at least 2-D with 
1's post-pended to the shape (column vectors made out of 1-D arrays). 

For detailed documentation, see `r_`. 

Examples 
-------- 
>>> np.c_[np.array([[1,2,3]]), 0, 0, np.array([[4,5,6]])] 
array([[1, 2, 3, 0, 0, 4, 5, 6]]) 

Answer 2

其實這是不是一個功能，它是類CClass的對象。

it is "not a function, so takes no parameters 

以上是官方文檔的說明。你可以檢查這個問題的細節。

numpy.r_ is not a function. What is it?