在 Python 字典中查找元素

Question

I am getting a python dictionary from AWS which is formatted like the following sample object:

{'ResponseMetadata': {'NOT IMPORTANT'},
 'hasMoreResults': True,
 'marker': '{"NOT IMPORTANT"}',
 'pipelineIdList': [{'id': 'df-0001',
                     'name': 'Blue'},
                    {'id': 'df-0002',
                     'name': 'Orange'},
                    {'id': 'df-0003',
                     'name': 'Green'},
                    {'id': 'df-0004',
                     'name': 'Red'},
                    {'id': 'df-0005',
                     'name': 'Purple'}
]}

I want to ask for the name of an input in pipelineIdList and get the id that matches with it. For example, if you search using the input string "Red" you will get a return value of "df-0004"

My code is as follows:

import boto3

def findId(pipeline_list, inputString):
  for dict in pipeline_list:
    if dict['pipelineIdList']['name'] == inputString:
      return dict['id']

def main():
  inputString = "Red"

  datapipeline = boto3.client('datapipeline')
  pipeline_list = datapipeline.list_pipelines() //This line returns a Dict like the one above

  result = findId(pipeline_list, inputString)
  print(result)


if __name__ == "__main__":
  main()

The print(result) in this case with inputString="Red" should print a value of df-0004 , but it instead prints absolutely nothing. Any help with fixing this issue would be greatly appreciated.

Answer 1

I normally approach problems like this by first writing a simple function. Once you understand the bare bones, you can get fancier and attempt code optimization via something like list comprehension, as suggested by @Maribeth Cogan.

def findId(obj_dictionary, color):
    lst = obj_dictionary['pipelineIdList']
    for dictionary in lst:
        if dictionary['name'] == color:
            return(dictionary['id'])

We extract the list we want to look at from the given dictionary, then go through the elements of that list to find the dictionary element whose value matches the given color target. Then, the method returns the key corresponding to that dictionary element.

Answer 2

a simple list comprehension can solve your problem. Try running this code:

my_color='Red'

result = [colorDict['id'] for colorDict in d['pipelineIdList'] if colorDict['name']==my_color][0]

the value of result should now be df-0004

Explanation : the list comprehension adds to a list the id of any dictionary in the pipelineIdList whose name property is the desired color. Since there is only one dictionary for the desired color, the length of the list is 1. Then you access the first (and only) element of that list, which has index 0.