for 循环和列表的问题答案

【问题标题】：Trouble with for loops and listsfor 循环和列表的问题
【发布时间】：2020-04-15 22:23:27
【问题描述】：

我正在制作一个将名为 param_list 的 3d 列表放在一起的函数。在函数的最后一个 for 循环中，所有列表值都是我想要的，但是在循环之外，值是错误的

def make_param_combos( params ):
   size = []
   param_list = []
   temp_params = []
   one_param = ['param','value']
   num_params = len( params )

   for j in range( num_params ) :

      if j == 0 :
        size.append( len(params[j][1] ) )
      else :
        size.append( len(params[j][1]) * size[j-1] ) 
        num_combos = size[j]

   for i in range( num_combos ) :

      temp_params.clear()

      for j in range( num_params ) :

         one_param = [ params[j][0], params[j][1][ int( np.mod( len( params[j][1] ) * i/size[j], len( params[j][1] ) ) ) ] ]

         temp_params.append( one_param )  

      param_list.append( temp_params )

      print( "loop iter", i, param_list[i] )

   print( "out of loop" )
   print( param_list )

   return param_list



plist = make_param_combos([[['param1'],['v11','v12']],[['param2'],['v21','v22']],[['param3'],['v31','v32']]]) 

print( "out of function" )

for i in range(len(plist)):
  print(plist[i])

结果：

循环迭代器 0 [[['param1'], 'v11'], [['param2'], 'v21'], [['param3'], 'v31']] 循环迭代器 1 [[['param1'], 'v12'], [['param2'], 'v21'], [['param3'], 'v31']]

循环迭代器 2 [[['param1'], 'v11'], [['param2'], 'v22'], [['param3'], 'v31']]

循环迭代 3 [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v31']]

循环迭代 4 [[['param1'], 'v11'], [['param2'], 'v21'], [['param3'], 'v32']]

循环迭代 5 [[['param1'], 'v12'], [['param2'], 'v21'], [['param3'], 'v32']]

循环迭代 6 [[['param1'], 'v11'], [['param2'], 'v22'], [['param3'], 'v32']]

循环迭代 7 [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

循环外 [[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']], [[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]]

功能失效

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

[[['param1'], 'v12'], [['param2'], 'v22'], [['param3'], 'v32']]

【问题讨论】：

标签： python list for-loop

【解决方案1】：

将temp_params.clear() 替换为temp_params = []。您需要一个新列表，.clear() 将从旧列表中删除所有元素 - 您刚刚附加到 param_list 的那个。您添加了此列表，即您现在正在清除的列表，而不是它的副本。

【讨论】：