Python dict.get() 在密钥存在且有效时抛出 KeyError

Question

I have a dict that maps strings to classes, so that they can be instantiated:

process_mapper = {VTNotifications.name: VTNotifications}

Where the class looks like:

class VTNotifications(AbstractNormaliser):

    # String name for use defining KV
    name = 'vt-notifications-feed'

    def __init__(self, config):
        super().__init__(config)
        self.config = config
        # Add source meta-data
        self.meta_normaliser = MetaDataNormaliser(source='vt-notifications', doc_type='notification',
                                                  event_type='vt-notification')

I've written a test that checks if the string does in fact return correctly, which passes:

def test_getter():
    class_type = process_mapper.get(VTNotifications.name)
    assert class_type == VTNotifications

However, when I attempt to pass pass the full config thats required to instantite the class, to a method does all the isntantiations, suddenly, it KeyErrors:

def test_mapped_normaliser():
    processor_name = VTNotifications.name
    normaliser = {'name': processor_name,
                  'config': {'consumer': {'topic': 'some_topic',
                                          'subscription': 'some_subscription'}},
                  'publisher': {'topic': 'some_other_topic'},
                  'project-id': 'some_id'}
    config = {'normalisers': [normaliser]}
    runner = NormaliserRunner(config)
    assert isinstance(runner.processes[processor_name], VTNotifications)



class NormaliserRunner(object):

    def __init__(self, config):
        self.normalisers = config['normalisers']
        self.processes = {}
        self.config = config
        self.map_processes()

    def run(self):
        for process in self.processes.values():
            process.normalise()

    # returns a dict of normaliser processes, and their mapped class implementations instantiated
    def map_processes(self):
        print(f"[*] Using processes mapper with {process_mapper.keys()} keys")
        for normaliser in self.normalisers:
            print(normaliser)
            self.processes[normaliser['name']] = process_mapper.get(
                normaliser['name'])(self.config[normaliser['name']]['config'])

============================= test session starts ==============================
platform linux -- Python 3.7.7, pytest-5.4.1, py-1.8.1, pluggy-0.13.1
rootdir: /mnt/c/Users/ARES/Desktop/work/phoenix/normaliser
collected 3 items

test.py ..F                                                              [100%]

=================================== FAILURES ===================================
____________________________ test_mapped_normaliser ____________________________

    def test_mapped_normaliser():
        processor_name = VTNotifications.name
        normaliser = {'name': processor_name,
                      'config': {'consumer': {'topic': 'some_topic',
                                              'subscription': 'some_subscription'}},
                      'publisher': {'topic': 'some_other_topic'},
                      'project-id': 'some_id'}
        config = {'normalisers': [normaliser]}
>       runner = NormaliserRunner(config)

test.py:31: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
main.py:14: in __init__
    self.map_processes()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <normaliser.main.NormaliserRunner object at 0x7ff3d0e7fc10>

    def map_processes(self):
        print(f"[*] Using processes mapper with {process_mapper.keys()} keys")
        for normaliser in self.normalisers:
            print(normaliser)
            self.processes[normaliser['name']] = process_mapper.get(
>               normaliser['name'])(self.config[normaliser['name']]['config'])
E           KeyError: 'vt-notifications-feed'

main.py:26: KeyError
----------------------------- Captured stdout call -----------------------------
[*] Using processes mapper with dict_keys(['vt-notifications-feed']) keys
{'name': 'vt-notifications-feed', 'config': {'consumer': {'topic': 'some_topic', 'subscription': 'some_subscription'}}, 'publisher': {'topic': 'some_other_topic'}, 'project-id': 'some_id'}
=========================== short test summary info ============================
FAILED test.py::test_mapped_normaliser - KeyError: 'vt-notifications-feed'
========================= 1 failed, 2 passed in 0.33s ==========================

You can even see it print the keys, and the required keys be there. So I'm not sure what Python is doing differently across the implementations that is causing this issue

Answer 1

You mixed up value and keys. There is a key-value pair with a value of 'vt-notifications-feed' , but its key is 'name'