Get only unique elements from two lists

Question

If I have two lists (may be with different len):

x = [1,2,3,4]
f = [1,11,22,33,44,3,4]

result = [11,22,33,44]

im doing:

for element in f:
    if element in x:
        f.remove(element)

I'm getting

result = [11,22,33,44,4]

Answer 1

UPDATE:

Thanks to @Ahito:

In : list(set(x).symmetric_difference(set(f)))

Out: [33, 2, 22, 11, 44]

This article has a neat diagram that explains what the symmetric difference does.

OLD answer:

Using this piece of Python's documentation on sets:

>>> # Demonstrate set operations on unique letters from two words
...
>>> a = set('abracadabra')
>>> b = set('alacazam')
>>> a                                  # unique letters in a
{'a', 'r', 'b', 'c', 'd'}
>>> a - b                              # letters in a but not in b
{'r', 'd', 'b'}
>>> a | b                              # letters in a or b or both
{'a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'}
>>> a & b                              # letters in both a and b
{'a', 'c'}
>>> a ^ b                              # letters in a or b but not both
{'r', 'd', 'b', 'm', 'z', 'l'}

I came up with this piece of code to obtain unique elements from two lists:

(set(x) | set(f)) - (set(x) & set(f))

or slightly modified to return list:

list((set(x) | set(f)) - (set(x) & set(f))) #if you need a list

Here:

1. | operator returns elements in x, f or both
2. & operator returns elements in both x and f
3. - operator subtracts the results of & from | and provides us with the elements that are uniquely presented only in one of the lists

Answer 2

If you want the unique elements from both lists, this should work:

x = [1,2,3,4]
f = [1,11,22,33,44,3,4]

res = list(set(x+f))
print(res)
# res = [1, 2, 3, 4, 33, 11, 44, 22]

Answer 3

Based on the clarification of this question in a new (closed) question:

If you want all items from the second list that do not appear in the first list you can write:

x = [1,2,3,4]
f = [1,11,22,33,44,3,4]

result = set(f) - set(x) # correct elements, but not yet in sorted order
print(sorted(result)) # sort and print

# Output: [11, 22, 33, 44]

Answer 4

x = [1, 2, 3, 4]

f = [1, 11, 22, 33, 44, 3, 4]

list(set(x) ^ set(f))

[33, 2, 22, 11, 44]

Answer 5

if you want to get only unique elements from the two list then you can get it by..

a=[1,2,3,4,5]
b= [2,4,1]
list(set(a) - set(b))
OP:- [3, 5]

Answer 6

Input :

x = [1,2,3,4]

f = [1,11,22,33,44,3,4]

Code:

l = list(set(x).symmetric_difference(set(f)))
print(l)

Output :

[2, 22, 33, 11, 44]

Answer 7

Your method won't get the unique element "2". What about:

list(set(x).intersection(f))

Answer 8

Simplified Version & in support of @iopheam's answer.

Use Set Subtraction.

# original list values
x = [1,2,3,4]
f = [1,11,22,33,44,3,4]

# updated to set's
y = set(x)  # {1, 2, 3, 4}
z = set(f)  # {1, 33, 3, 4, 11, 44, 22}

# parsed to the result variable
result = z - y  # {33, 11, 44, 22}

# printed using the sorted() function to display as requested/stated by the op.
print(f"Result of f - x: {sorted(result)}")
# Result of f - x: [11, 22, 33, 44]

Answer 9

v_child_value = [{'a':1}, {'b':2}, {'v':22}, {'bb':23}]
shop_by_cat_sub_cats = [{'a':1}, {'b':2}, {'bbb':222}, {'bb':23}]


unique_sub_cats = []
for ind in shop_by_cat_sub_cats:
    if ind not in v_child_value:
        unique_sub_cats.append(ind)

unique_sub_cats = [{'bbb': 222}]

Answer 10

Python code to create a unique list from two lists :

a=[1,1,2,3,5,1,8,13,6,21,34,55,89,1,2,3]
b=[1,2,3,4,5,6,7,8,9,10,11,12,2,3,4]
m=list(dict.fromkeys([a[i] for i in range(0,len(a)) if a [i] in a and a[i] in b and a[i]]))

print(m)

Answer 11

L=[] 
For i in x:
    If i not in f:
        L. Append(I)
For i in f:
    If I not in x:
        L. Append(I)
Return L