如何在Python中使用循环遍历字典列表并提取部分数值？

huangapple
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英文:

How can I iterate through a list of dictionaries and extract a subset of values in Python using loops?

问题

我有一个Python列表，如下所示：

  1. data_list等于字典对象中的“values”键，该字典对象是一个项目列表
  3. "values": [
  4.     {
  5.         "a": 1,
  6.         "b": 2,
  7.         "center code here": 3,
  8.         "d": 4
  9.     },
  10.     {
  11.         "a": 1,
  12.         "b": 2,
  13.         "c": 3,
  14.         "d": 4
  15.     },
  16.     {
  17.         "a": 1,
  18.         "b": 2,
  19.         "c": 3,
  20.         "d": 4
  21.     },
  22.     {
  23.         "a": 1,
  24.         "b": 2,
  25.         "c": 3,
  26.         "d": 4
  27.     }
  28. ]

我还有另一个列表，其中包含我想要的值：

  1. listx = ["a", "b"]

这是我尝试过的代码：

  1. listx = ["a", "b"]
  2. dict2 = {}
  4. for d in data_list:
  5.     for v, x in d.items():
  6.         if v in listx:
  7.             dict2[v] = x
  9. print(len(dict2))

我得到的结果是12，这是一个字典中的项目数。它没有遍历其他字典。有人可以帮忙吗？

我的目标是能够创建一个具有以下值的列表子集：

  1. "values": [
  2.     {
  3.         "a": 1,
  4.         "b": 2
  5.     },
  6.     {
  7.         "a": 1,
  8.         "b": 2
  9.     },
  10.     {
  11.         "a": 1,
  12.         "b": 2
  13.     },
  14.     {
  15.         "a": 1,
  16.         "b": 2
  17.     }
  18. ]

有人可以帮助我吗？我做错了什么？

英文:

Iterate through a list of dictionaries to get subset

I have a python list as follows:

data_list is equivalent to values key
in a dictionary object which is a list of items

  1.  "values": [
  2.         {
  3.             "a": 1,
  4.             "b": 2,
  5.             "center code here": 3,
  6.             "d": 4,
  7.         },
  8.         {
  9.             "a": 1,
  10.             "b": 2,
  11.             "c": 3
  12.             "d": 4,
  13.         },
  14.         {
  15.             "a": 1,
  16.             "b": 2,
  17.             "c": 3
  18.             "d": 4,
  19.         },
  20.         {
  21.             "a": 1,
  22.             "b": 2,
  23.             "c": 3
  24.             "d": 4,
  26.         }
  27.     ]

I also have another list that holds the values i want

  1. listx = [a,b]

This is what i tried :

  1.  listx = [a,b]
  2.  dict2 = {}    
  3.                 
  4.  for d in data_list:     
  5.      for v,x in d.items(): 
  6.           if v in listx:
  7.               dict2[v] = (x)
  8.                 
  9.  print(len(dict2))

I get 12 which is the number of items in one dictionary. It doesn't iterate over the other dictionaries?
Can anyone help ?

My goal is to be able to create a subset of this list with the following values :

  1.      "values": [
  2.         {
  3.             "a": 1,
  4.             "b": 2
  5.         },
  6.         {
  7.             "a": 1,
  8.             "b": 2
  9.         },
  10.         {
  11.             "a": 1,
  12.             "b": 2
  13.         },
  14.         {
  15.             "a": 1,
  16.             "b": 2
  18.         }
  19.     ]

Can anyone help me here ? What am i doping wrong?

答案1

得分: 3

以下是您要翻译的代码部分：

  1. values = [
  2.     {
  3.         "a": 1,
  4.         "b": 2,
  5.         "c": 3,
  6.         "d": 4,
  7.     },
  8.     {
  9.         "a": 1,
  10.         "b": 2,
  11.         "c": 3,
  12.         "d": 4,
  13.     },
  14.     {
  15.         "a": 1,
  16.         "b": 2,
  17.         "c": 3,
  18.         "d": 4,
  19.     },
  20.     {
  21.         "a": 1,
  22.         "b": 2,
  23.         "c": 3,
  24.         "d": 4,
  25.     },
  26. ]
  28. listx = ["a", "b"]
  30. values_filtered = [{k: v for k, v in d.items() if k in listx} for d in values]
  31. print(values_filtered)

输出：

  1. [
  2.  {"a": 1, "b": 2}, 
  3.  {"a": 1, "b": 2}, 
  4.  {"a": 1, "b": 2}, 
  5.  {"a": 1, "b": 2}
  6. ]
英文:

You can use simple list comprehension to filter the values:

  1. values = [
  2.     {
  3.         "a": 1,
  4.         "b": 2,
  5.         "c": 3,
  6.         "d": 4,
  7.     },
  8.     {
  9.         "a": 1,
  10.         "b": 2,
  11.         "c": 3,
  12.         "d": 4,
  13.     },
  14.     {
  15.         "a": 1,
  16.         "b": 2,
  17.         "c": 3,
  18.         "d": 4,
  19.     },
  20.     {
  21.         "a": 1,
  22.         "b": 2,
  23.         "c": 3,
  24.         "d": 4,
  25.     },
  26. ]
  28. listx = ["a", "b"]
  30. values_filtered = [{k: v for k, v in d.items() if k in listx} for d in values]
  31. print(values_filtered)

Prints:

  1. [
  2.  {"a": 1, "b": 2}, 
  3.  {"a": 1, "b": 2}, 
  4.  {"a": 1, "b": 2}, 
  5.  {"a": 1, "b": 2}
  6. ]

答案2

得分: 2

以下是您提供的Python代码的翻译部分：

  1. listx = ["a", "b"]
  2. subset = []
  4. for d in data_list:
  5.     subset_dict = {}
  6.     for key, value in d.items():
  7.         if key in listx:
  8.             subset_dict[key] = value
  9.     subset.append(subset_dict)
  11. print(subset)

输出:

  1. [{'a': 1, 'b': 2}, {'a': 1, 'b': 2}, {'a': 1, 'b': 2}, {'a': 1, 'b': 2}]

或者您可以使用itemgetter：

  1. from operator import itemgetter
  3. listx = ["a", "b"]
  4. subset = [dict(zip(listx, itemgetter(*listx)(d))) for d in data_list]
  5. print(subset)
英文: 
  1. listx = ["a", "b"]
  2. subset = []
  4. for d in data_list:
  5.     subset_dict = {}
  6.     for key, value in d.items():
  7.         if key in listx:
  8.             subset_dict[key] = value
  9.     subset.append(subset_dict)
  11. print(subset)

Output:

  1. [{'a': 1, 'b': 2}, {'a': 1, 'b': 2}, {'a': 1, 'b': 2}, {'a': 1, 'b': 2}]

Or you can use itemgetter:

  1. from operator import itemgetter
  3. listx = ["a", "b"]
  4. subset = [dict(zip(listx, itemgetter(*listx)(d))) for d in data_list]
  5. print(subset)

huangapple
  • 本文由 发表于 2023年6月1日 05:08:31
  • 转载请务必保留本文链接：https://go.coder-hub.com/76377316.html
  • dictionary
  • list
  • loops
  • python
  • subset
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