CODEWITHSUNDEEP
pythonlistdictionaryfor-loopzip
blah
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Reputation: 664

How to iterate through 2 zipped list of dictionaries under certain conditions?

There are 4 list of dictionaries, the first two need to be added to the database, the second 2 already exist in the database:

to_add1 = [{'name': 'Kate', 'age': 25, 'id': 1234},
           {'name': 'Claire', 'age': 25, 'id': 4567},
           {'name': 'Bob', 'age': 25, 'id': 8910}]

to_add2 = [{'pets': 5, 'name_id': 1234},
           {'pets': 0, 'name_id': 4567},
           {'pets': 0, 'name_id': 8910}]

existing1 = [{'name': 'John', 'age': 50, 'id': 0000},
             {'name': 'Claire', 'age': 25, 'id': 4567}]
existing2 = [{'pets': 2, 'name_id': 0000},
             {'pets': 0, 'name_id': 4567}]

I would like to add to the database or in this reproducible example, print only the items that do not contain the existing1['name'] value in existing1. So in this case: Kate and Bob from to_add1 should be printed once. Due to the double loop, I am getting repetitions. How can I loop through all these dictionaries and print the items that do have a matching name to the names ofexisting 1 without repetitions ?

My code:

for person_to_add, pet_to_add in zip(to_add1, to_add2):
    for existing_person, existing_pet in zip(existing1, existing2):
        if person_to_add['name'] not in existing_person['name']:
            print(person_to_add)

Current output:

{'name': 'Kate', 'age': 25, 'id': 1234}
{'name': 'Kate', 'age': 25, 'id': 1234}
{'name': 'Claire', 'age': 25, 'id': 4567}
{'name': 'Bob', 'age': 25, 'id': 8910}
{'name': 'Bob', 'age': 25, 'id': 8910}

Desired output:

{'name': 'Kate', 'age': 25, 'id': 4567}
{'name': 'Bob', 'age': 25, 'id': 8910}

Upvotes: 0

Views: 54

Answers (3)

Meghraj pardesi
Meghraj pardesi

Reputation: 86

lst = [print(person_to_add) for person_to_add in to_add1 if person_to_add not in existing1]

It might not the fastest solution but it get the job done. it uses python list comprehension, and easy to read.

As you described in the problem that you only want to compare data in existing1 and to_add1 so you don't need use nested loops adding unnecessary complexity. you will be fine using a single loop.

Upvotes: 1

Jason Chia
Jason Chia

Reputation: 1145

Depending on the complexity of the actual underlying query this might not work. But here is a solution taking advantage of the list of dictionary structure you are using. It is unclear exactly to me why you would need to use zip.

a = [person_to_add for person_to_add in to_add1 if person_to_add['name'] not in [existing_person['name'] for existing_person in existing1]]

This uses list comprehensions which should be pretty fast. The output 'a' would be in the same format as all your other data i.e a list of dicts. Do let me know if you need a further breakdown on how the list comprehension works.

Upvotes: 1

yvesonline
yvesonline

Reputation: 4837

I assume you mean the output should be Kate & Bob because Claire is in existing1:

>>> for person_to_add, pet_to_add in zip(to_add1, to_add2):
...     if person_to_add not in existing1:
...         print(person_to_add)
... 
{'name': 'Kate', 'age': 25, 'id': 1234}
{'name': 'Bob', 'age': 25, 'id': 8910}

Upvotes: 1

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