CODEWITHSUNDEEP
pythonlistgrouping
Mp0int
Mp0int

Reputation: 18727

Grouping elements according to a single value

I have a list of "Bank application type" "bank name" and their local ID values. like:

BANKS = [
    (1, "Bank A Web", "BankA"),
    (2, "Bank B ATM", "BankB"),
    (3, "Bank A Wap", "BankA"),    
    (4, "Bank C",     "BankC"),
]

I want to categorize their IDs according to their bank name so I used a simplified list for this purpose

BANKS_CATS = [
    (1, "BankA"),
    (2, "BankB"),
    (3, "BankA"), 
    (4, "BankC"),
]

I want to match each bank Id with other associated bank IDs (different services from the same bank)

{1: [1, 3],
 2: [2],
 3: [1, 3],
 4: [4]}

Also that value list is a simplified example, my actual bank names and bank service names are different and do not have a similar pattern to match to categorize them.

I ordered my actual list 

my_new_list = sorted(BANKS_CATS, key=lambda s: s[1])

then try to group it

from itertools import groupby
grouped = groupby(my_new_list, key=lambda s: s[1])

but form that point on, I could not achieve what I want.. I try to iterate over the grouped values with no success.

How can I achieve required result from this point?

Upvotes: 1

Views: 105

Answers (2)

thefourtheye
thefourtheye

Reputation: 239443

my_list = [
    (1, "BankA"),
    (2, "BankB"),
    (3, "BankA"), 
    (4, "BankC"),
]

ids, result = {}, {}
for num, bank in my_list: ids.setdefault(bank, []).append (num)
for num, bank in my_list: result[num] = ids[bank]
print result

Output

{1: [1, 3], 2: [2], 3: [1, 3], 4: [4]}

Upvotes: 2

Pooya Eghbali
Pooya Eghbali

Reputation: 209

This is a one line code without dependencies:

{int(t[1][4:]):[i[0] for i in my_list if i[1] == t[1]] for t in my_list}

first gathers groups from my_list, and then finds values in my_list for each group.

Upvotes: 0

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