NumPy append बनाम concatenate

Question

NumPy append और concatenate के बीच क्या अंतर है?

मेरा अवलोकन यह है कि concatenate थोड़ा तेज़ है और append अक्ष निर्दिष्ट नहीं होने पर सरणी को फ़्लैट करता है।

In [52]: print a 
[[1 2] 
[3 4] 
[5 6] 
[5 6] 
[1 2] 
[3 4] 
[5 6] 
[5 6] 
[1 2] 
[3 4] 
[5 6] 
[5 6] 
[5 6]] 

In [53]: print b 
[[1 2] 
[3 4] 
[5 6] 
[5 6] 
[1 2] 
[3 4] 
[5 6] 
[5 6] 
[5 6]] 

In [54]: timeit -n 10000 -r 5 np.concatenate((a, b)) 
10000 loops, best of 5: 2.05 µs per loop 

In [55]: timeit -n 10000 -r 5 np.append(a, b, axis = 0) 
10000 loops, best of 5: 2.41 µs per loop 

In [58]: np.concatenate((a, b)) 
Out[58]: 
array([[1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [5, 6]]) 

In [59]: np.append(a, b, axis = 0) 
Out[59]: 
array([[1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [1, 2], 
     [3, 4], 
     [5, 6], 
     [5, 6], 
     [5, 6]]) 

In [60]: np.append(a, b) 
Out[60]: 
array([1, 2, 3, 4, 5, 6, 5, 6, 1, 2, 3, 4, 5, 6, 5, 6, 1, 2, 3, 4, 5, 6, 5, 
     6, 5, 6, 1, 2, 3, 4, 5, 6, 5, 6, 1, 2, 3, 4, 5, 6, 5, 6, 5, 6]) 

Answer 1

np.appendnp.concatenate उपयोग करता है:

def append(arr, values, axis=None): 
    arr = asanyarray(arr) 
    if axis is None: 
     if arr.ndim != 1: 
      arr = arr.ravel() 
     values = ravel(values) 
     axis = arr.ndim-1 
    return concatenate((arr, values), axis=axis)