Configuring an object via a dictionary
Grant Edwards
grant.b.edwards at gmail.com
Fri Mar 15 15:09:43 EDT 2024
On 2024-03-15, Thomas Passin via Python-list <python-list at python.org> wrote:
> On 3/15/2024 5:30 AM, Loris Bennett via Python-list wrote:
>> Hi,
>>
>> I am initialising an object via the following:
>>
>> def __init__(self, config):
>>
>> self.connection = None
>>
>> self.source_name = config['source_name']
>> self.server_host = config['server_host']
>> self.server_port = config['server_port']
>> self.user_base = config['user_base']
>> self.user_identifier = config['user_identifier']
>> self.group_base = config['group_base']
>> self.group_identifier = config['group_identifier']
>> self.owner_base = config['owner_base']
>>
>> However, some entries in the configuration might be missing. What is
>> the best way of dealing with this?
>>
>> I could of course simply test each element of the dictionary before
>> trying to use. I could also just write
>>
>> self.config = config
>>
>> but then addressing the elements will add more clutter to the code.
>>
>> However, with a view to asking forgiveness rather than
>> permission, is there some simple way just to assign the dictionary
>> elements which do in fact exist to self-variables?
>>
>> Or should I be doing this completely differently?
>
> self.source_name = config.get('source_name', default_value)
>
> Or, if you like this kind of expression better,
>
> self.source_name = config.get('source_name') or default_value
Won't the latter version misbehave if the value of config['source_name'] has a
"false" boolean value (e.g. "", 0, 0.0, None, [], (), {}, ...)
>>> config = {}
>>> config['source_name'] = ""
>>> config.get('source_name') or 'default'
'default'
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