0 ::和0之間有什麼區別：過濾一個numpy數組？

Question

我正在嘗試使用Python和NumPy解決問題的Kaggle Titanic tutorial。我很難理解數據[0 ::，]和數據[0 :,]之間的區別。我複製粘貼下面的相關代碼片段：

for i in xrange(number_of_classes):  #loop through each class 
    for j in xrange(number_of_price_brackets): #loop through each price bin 

     women_only_stats = data[       # Which element   
           (data[0::, 4] == "female") & # is a female and 
           (data[0::, 2].astype(np.float) # was ith class 
            == i+1) 
           &        # and 
           (data[0:, 9].astype(np.float) # was greater 
            >= j * fare_bracket_size) # than this bin 
           &        # and 
           (data[0:, 9].astype(np.float) # less than 
            < (j+1)*fare_bracket_size) # the next bin  
           , 1]      # in the 2nd col 

Answer 1

沒有區別，這兩種方法將鉤到__getitem__以同樣的方式。

>>> class Thing(object): 
...  def __getitem__(self, item): 
...   print(repr(item)) 
... 
>>> t = Thing() 
>>> t[0:, 4] 
(slice(0, None, None), 4) 
>>> t[0::, 4] 
(slice(0, None, None), 4)