How to check in Python if the value in a key value pair of a dict is a list or a string

Question

I have an object like this

ds_obj = {
              "Labels" : 
                [ 
                    {
                        "Label" : "pop",
                        "People" : {
                          "Composer" : "John"
                        },
                    },
                    {
                        "Label" : "classical",
                        "People" : {
                          "Composer" : [ "Johann", "Jason" ]
                        },
                    },
                    {
                        "Label" : "classical-2",
                        "People" : {
                          "Composer" : [ "Jacob" ]
                        },
                    }        
                ]
            }

I need to iterate thru each of the labels and perform some actions on each of the composers, but first I need to find out if each label has a single composer or multiple. To do this I am running the following code to find out if the key Composer has an array or a string. If it has an array, I will run a nested loop thru it and work with each composer. The code below however is calling out every value as an array. What is wrong with my code? Is there a more efficient way to do this?

    for label in ds_obj ['Labels']:
        if hasattr(label['People']['Composer'], "__len__"):
            print('IS ARRAY')
        else:
            print('NOT Array')

Asked By: user20358

||

Source

Answer 1

Use:

if isinstance(label['People']['Composer'], list):

Python strings also have a __len__ attribute so your code is true for both lists and strings.

Answered By: Jeff

Answer 2

You’re currently checking if composer has a length. Both strings and lists have lengths, so hasattr(..., '__len__') will return True in both cases.

You can just check if the type is equal to List.:

for label in ds_obj ['Labels']:
    if type(label['People']['Composer']) is list:
        print('Array')
    else: 
        print('NOT Array')

Answered By: ae_bu

How to check in Python if the value in a key value pair of a dict is a list or a string

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