如何在Python中創建映射列表（關聯子數組）

Question

我是Python的n00b，並試圖將我從shell和PHP腳本中獲得的知識帶入Python。我真的很想掌握創建和操作內部值的概念（同時保持代碼的可理解形式）。

我無法使用LISTS和MAPPINGS（dict（））的Python實現。我正在編寫一個腳本，需要在基本數組（Python列表）內使用關聯數組（一個python映射）。該列表可以使用典型的INT索引。

謝謝！

這裏是我目前：

''' Marrying old-school array concepts 
[in Python verbiage] a list (arr1) of mappings (arr2) 
[per my old-school training] a 2D array with 
     arr1 using an INT index 
     arr2 using an associative index 
''' 
arr1 = [] 
arr1[0] = dict([ ('ticker'," "), 
         ('t_date'," "), 
         ('t_open'," "), 
         ('t_high'," "), 
         ('t_low'," "), 
         ('t_close'," "), 
         ('t_volume'," ") 
         ]) 
arr1[1] = dict([ ('ticker'," "), 
         ('t_date'," "), 
         ('t_open'," "), 
         ('t_high'," "), 
         ('t_low'," "), 
         ('t_close'," "), 
         ('t_volume'," ") 
         ]) 

arr1[0]['t_volume'] = 11250000 
arr1[1]['t_volume'] = 11260000 

print "\nAssociative array inside of an INT indexed array:" 
print arr1[0]['t_volume'], arr1[1]['t_volume'] 

在PHP中，我有以下示例工作：

''' 
arr_desired[0] = array('ticker'  => 'ibm' 
          't_date'  => '1/1/2008' 
          't_open'  => 123.20 
          't_high'  => 123.20 
          't_low'  => 123.20 
          't_close' => 123.20 
          't_volume' => 11250000 
         ); 
arr_desired[1] = array('ticker'  => 'ibm' 
          't_date'  => '1/2/2008' 
          't_open'  => 124.20 
          't_high'  => 124.20 
          't_low'  => 124.20 
          't_close' => 124.20 
          't_volume' => 11260000 
         ); 

print arr_desired[0]['t_volume'],arr_desired[1]['t_volume'] # should print>>> 11250000 11260000 
''' 

Answer 1

你的列表和字典字面定義，可以大大簡化：

keys = ['ticker', 't_date', 't_open', 't_high', 't_low', 't_close', 't_volume'] 
arr1 = [ 
    dict.fromkeys(keys, ' '), 
    dict.fromkeys(keys, ' ') 
] 

我正在使用dict.fromkeys()方法初始化一個字典與一系列的鍵，所有與給定的默認值（一個空格字符串）。

當你在Python中定義一個空列表時，你不能簡單地處理不存在的元素。或者，使用.append()方法新元素添加到列表：

arr1.append({'key': 'value', 'otherkey': 'othervalue'}) 

上面的示例使用{k: v}字典的文字符號。

我懷疑你會受益於首先閱讀（優秀）Python tutorial。

Answer 2

這是我學到的東西，對於那些從類似的編程背景的礦山：

arr0 = dict([ ('one',1), ('two',2), ('three',3) ]) 
for k,v in arr0.iteritems() : 
    print k,v   #prints the associative array key with the value 

keys = ['ticker','t_open','t_high','t_low','t_close','t_volume'] 
arr1 = [ 
      dict.fromkeys(keys,' '), 
      dict.fromkeys(keys,' ') 
     ] 

arr1[0]['t_volume'] = 11250000 
arr1[1]['t_volume'] = 11260000 
arr1.append({'ticker' : 'ibm', 't_date' : '1/2/2008', 't_volume' : 11270000}) 
arr1.insert(3, {'ticker' : 'ibm', 't_date' : '1/3/2008', 't_volume' : 11280000}) 

print "\nAssociative array inside of an INT indexed array:" 
print arr1[0]['t_volume'], arr1[1]['t_volume'] 
print "\n ",arr1[2] 
print arr1[2]['t_volume'], arr1[3]['t_volume'] 

注意的元素（值），另外的邏輯。