Compare list items inside dictionary

Question

Good day ! I am having some trouble comparing values inside lists that are inside a dictionary.

{'lst_4':['New York', 'Amsterdam', 'Berlin'],'lst_5':['New York', 'Brussels', 
Rome'],'lst_6':['Helsinki', 'Stockholm', Milan']}

The final goal is to compare the first item in each list, if they match I want to print which one it was. However I am having trouble comparing them because of the dict/listception.

My code so far:

x = 0
dct = {}
for row_cells in sheet.iter_rows(min_row=1, max_row=20):
    x += 1
    dct['lst_%s' %x] = []
    for cell in row_cells:
        if cell.value == None:
            break
        else:
            dct['lst_%s' %x].append(cell.value) 
    print("-------------------------------------------------")
    if not dct['lst_%s' %x]:
        break
    zin = dct['lst_%s' %x][0:]
    print(zin)

Any help, or pointers are much appreciated.

Cheers,

Possible duplicate of [Is there a better way to compare dictionary values](https://stackoverflow.com/questions/1911273/is-there-a-better-way-to-compare-dictionary-values) — TobiSH, Mar 08 '18 at 13:37
Can you show what you have done so far? Then the hints can be much more specific. — lkriener, Mar 08 '18 at 13:38
@TobiSH hm, there he compares Dict values, they are not inside lists if Im not mistaken — toom, Mar 08 '18 at 13:40
@TobiSH Compare the first item of multiple lists inside a single dictionary — toom, Mar 08 '18 at 13:45
Do you want to verify that there is a duplicate city, or you want all first items to have the same city name? — Vasilis G., Mar 08 '18 at 13:50
I want to check if multiple lists have the first same item. Not all lists have to match it — toom, Mar 08 '18 at 13:52

vvvvv · Accepted Answer · 2018-03-08T13:51:49.937

If your goal is to detect if every list has the same first element, just do:

my_dict = {'lst_4':['New York', 'Amsterdam', 'Berlin'],
       'lst_5':['New York', 'Brussels', 'Rome'],
       'lst_6':['Helsinki', 'Stockholm', 'Milan']}

keys = list(my_dict.keys())

if all([my_dict[k][0] == my_dict[keys[0]][0] for k in keys]):
    print(my_dict[keys[0]][0])

In your example, there would be no output.

But if you want to find if 2 lists have the same first element, you could do something like:

my_dict = {'lst_4':['New York', 'Amsterdam', 'Berlin'],
           'lst_5':['New York', 'Brussels', 'Rome'],
           'lst_6':['Helsinki', 'Stockholm', 'Milan']}

keys = list(my_dict.keys())
for i, k1 in enumerate(keys):
    for j, k2 in enumerate(keys[i+1:]):
        if my_dict[k1][0] == my_dict[k2][0]:
            print(my_dict[k1][0])

In your case, the output is:

"New York"

You iterate over the lists to find if a couple of lists have the same first element.

My bad, any duplicates should be printed so Im gonna give this one a try — toom, Mar 08 '18 at 13:50

score 2 · Answer 2 · answered Mar 08 '18 at 13:54

2

I would use itertools.combinations for this:

from itertools import combinations

for one, two in combinations(dct, 2):
    if dct[one][0] == dct[two][0]:
        print("Both", one, "and", two, "have", dct[one][0])

answered Mar 08 '18 at 13:54

L3viathan

26,748
2
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score 1 · Answer 3 · answered Mar 08 '18 at 13:48

You could try this:

d = {'lst_4':['New York', 'Amsterdam', 'Berlin'],'lst_5':['New York', 'Brussels', 'Rome'],'lst_6':['Helsinki', 'Stockholm', 'Milan']}


def findDuplicateFirstItem(dictionary):
    s = set()
    for value in dictionary.values():
        if value[0] not in s:
            s.add(value[0])
        else:
            print(value[0])

findDuplicateFirstItem(d)

>>>New York

Compare list items inside dictionary

3 Answers3