CODEWITHSUNDEEP
pythondictionary
whyeliah
whyeliah

Reputation: 95

Rename Keys that May or May Not Exist (Python)

I am taking a data set with each entry classified with a numeric code. Only the first 2-digits are needed, so I'm summing based on just those. 

sum_dict = {
    k: sum(item[1] for item in g) 
    for k, g in groupby(sorted(
        source_data.items()), key=lambda item: item[0][:2])
}

There's a known number of categories, but all categories are not necessarily used in every instance. The sum_dict will only have entries for the 2-digit category if it appeared in the source data.

sum_dict = {
    '12': 15,
    '29': 3,
    '33': 22,
}

I want to change all the keys in sum_dict to be more descriptive, so I am deleting each key and replacing it with a more descriptive one. However, there will be a key error if a particular instance of the dictionary does not use a key that I then rename ('65' in this example).

if '12'in sum_dict:
    sum_dict['12: Alpha'] = sum_dict.pop('12')
if '29'in sum_dict:
    sum_dict['29: Beta'] = sum_dict.pop('29')
if '33'in sum_dict:
    sum_dict['33: Gamma'] = sum_dict.pop('33')
if '65'in sum_dict:
    sum_dict['65: Delta'] = sum_dict.pop('65')

I added the if checks so I could rename all possible keys even if they don't exist every time, but it seems inefficient (and harder to read) to have dozens of ifs to do this task. Am I missing a better way of doing this?

Upvotes: 0

Views: 177

Answers (2)

Martijn Pieters
Martijn Pieters

Reputation: 1122312

Create a mapping for your names:

better_names = {'12': 'Alpha', '29': 'Beta', '33': 'Gamma', '65': 'Delta'}

Now you can use these when producing your initial dictionary, no renaming needed:

sum_dict = {
    '{}: {}'.format(k, better_names[k]): sum(item[1] for item in g) 
    for k, g in groupby(sorted(
        source_data.items()), key=lambda item: item[0][:2])
}

However, if you must rename later on, you can use that same dictionary in a loop:

for key, name in better_names.items():
    if key in sum_dict:
        sum_dict['{}: {}'.format(key, name)] = sum_dict.pop(key)

Upvotes: 1

Jules
Jules

Reputation: 973

variable_array = [("12", "Alpha"),("29", "Beta") ... ("65","Delta")]
for number, var in variable_array:
    if number in sum_dict:
        sum_dict["{}: {}".format(number, var)] = sum_dict.pop(number)

This should do what you want

Upvotes: 2

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