Python - Flatting Dictionary where some keys are 'missing'

Is there a cleaner way to do this? I am checking a nested dictionary for a specific key and assigning that to a variable. I will be using it to make a mysql insert shortly.

My main issue is that if the key is not present (which sometimes happens) I dont want the code to fail, I just want to sent the variable to empty.

This code seems to work but I have to do something similar to about 20 differnt key values so I would like to make sure I am doing it the best way

if 'Model' in ItemAttributes:
Model=ItemAttributes['Model']['value']
else:
Model=''


3 Answers
3

Here is one solution:

Model = ItemAttributes.get('Model', {}).get('value', '')


If the "Model" key does not exist in the ItemAttributes dictionary, you return an empty dictionary, on which you use dict.get('value', ''). This will, of course, return an empty string if the "Model" key does not exist.

ItemAttributes

dict.get('value', '')

An alternative solution is to add an extra function call and have this function test for whether the key exists. Here we use a ternary statement. This is effectively what you are doing now, but wrapping the logic in a function for easy repeated access:

def get_value(d, key1, key2):
return d[key1][key2] if key1 in d else ''

Model = get_value(ItemAttributes, 'Model', 'value')


A more generic solution is to use try / except and catch KeyError. If any key is missing, the function will return an empty string. Otherwise, reduce + getitem will cycle through the nested dictionary to access the appropriate value given a list of keys.

try

except

KeyError

reduce

getitem

from functools import reduce
from operator import getitem

def getFromDict(dataDict, mapList):
try:
return reduce(getitem, mapList, dataDict)
except KeyError:
return ''

Model = getFromDict(ItemAttributes, ['Model', 'Value'])


model = ItemAttributes.get('Model', {}).get('value', '')


Not sure if it's much better, but it works! :)

Using get is often the best solution.
Another solution is to catch KeyErrorexception:

KeyError

try:
Model=ItemAttributes['Model']['value']
except KeyError:
Model=''


Model will be set to '' if 'Model' is not in ItemAttributes or if 'value' is not in ItemAttributes['Model']

''

'Model'

ItemAttributes

'value'

ItemAttributes['Model']

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