finding common elements between two lists?

Question

I have two lists that are formatted as so:

sortedAlt=[['TIF35', 'TIF35'], ['PTP1', 'SSM4'], ['AMD1', 'PRP40'], ['END3', 'RAD26']]
sortedB=[['SDP1', 'SLT2'], ['ATG34', 'GCD7'], ['END3', 'RAD26'], ['TIF35', 'TIF35']]

and I need to find the shared elements between the two lists. I have tried a couple things:

These two return only []:

sharedEdges = []
temp = [sharedEdges.add((a, b)) for (a, b) in sortedB  
              if (a, b) in sortedAlt]

for (a,b) in sortedAlt:
    print((a,b))
    if (a,b) in sortedB:
        sharedEdges.add((a,b))
print(sharedEdges)

For the above code, I'm pretty sure the issue is within the if statement; if I used the same list input for both, I still get an empty output.

If I try to use the intersection function, I get the error: TypeError: unhashable type: 'list'

sharedEdges = set(sortedAlt) & set(sortedB)
sharedEdges = list(set(sortedAlt)-set(sortedAlt))
print(sharedEdges)

Answer 1

Convert the inner lists to tuples, so they are hashable. Then you can use

sortedAlt=[['TIF35', 'TIF35'], ['PTP1', 'SSM4'], ['AMD1', 'PRP40'], ['END3', 'RAD26']]
sortedB=[['SDP1', 'SLT2'], ['ATG34', 'GCD7'], ['END3', 'RAD26'], ['TIF35', 'TIF35']]

sharedEdges = set(tuple(i) for i in sortedAlt).intersection( (tuple(i) for i in sortedB))
print(sharedEdges)

Output:

{('END3', 'RAD26'), ('TIF35', 'TIF35')}

This is faster for bigger lists then using a list comprehension with in and probably on par with OlvinRoghts commented map - solution:

 # slightly modified from OlvinRoght comment on the question: s = list(map(list, set(map(tuple, sortedAlt)).intersection(map(tuple, sortedB)))) # [['TIF35', 'TIF35'], ['END3', 'RAD26']]

Answer 2

considering inner array element can be non sorted way, sorting them according to the character order then comparing

A=[['TIF35', 'TIF35'], ['PTP1', 'SSM4'], ['AMD1', 'PRP40'], ['END3', 'RAD26']]
B=[['SDP1', 'SLT2'], ['ATG34', 'GCD7'], ['END3', 'RAD26'], ['TIF35', 'TIF35']]

tmp_b = [sorted(inner_list) for inner_list in B]
res = []
for inner_list in A:
    if sorted(inner_list) in tmp_b:
        res.append(inner_list)

print(res)
#OUTPUT  [['TIF35', 'TIF35'], ['END3', 'RAD26']]

considering the inner list order of element not matter then using set operation as suggested by @patrickartner, this will make time complexit small

res = list(set(tuple(i) for i in A).intersection(set(tuple(i) for i in B)))

Answer 3

below (convert the list to tuple and use set)

sortedAlt=[['TIF35', 'TIF35'], ['PTP1', 'SSM4'], ['AMD1', 'PRP40'], ['END3', 'RAD26']]
sortedB=[['SDP1', 'SLT2'], ['ATG34', 'GCD7'], ['END3', 'RAD26'], ['TIF35', 'TIF35']]

sortedAltTuple = set(tuple(x) for x in sortedAlt)
sortedBTuple = set(tuple(x) for x in sortedB)
intersections = sortedAltTuple.intersection(sortedBTuple)
print(intersections)

output

{('END3', 'RAD26'), ('TIF35', 'TIF35')}

Answer 4

The simpler way is with sets indeed but set accepts hashable objects only . Lists are not hashable but tuples are. So the simpler is simply to cast lists to tuples before constructing sets.

shared_edges = set(map(tuple, sorted_alt)) & set(map(tuple, sorted_b))
shared_edges = list(map(list, shared_edges))  # then go back to lists if you want

By the way, please use the snake case ( shared_edges ) rather than the mixed case ( sharedEdges ). This is Python coding convention, see PEP8 .

Answer 5

I have two lists that are formatted as so:

sortedAlt=[['TIF35', 'TIF35'], ['PTP1', 'SSM4'], ['AMD1', 'PRP40'], ['END3', 'RAD26']]
sortedB=[['SDP1', 'SLT2'], ['ATG34', 'GCD7'], ['END3', 'RAD26'], ['TIF35', 'TIF35']]

and I need to find the shared elements between the two lists. I have tried a couple things:

These two return only []:

sharedEdges = []
temp = [sharedEdges.add((a, b)) for (a, b) in sortedB  
              if (a, b) in sortedAlt]

for (a,b) in sortedAlt:
    print((a,b))
    if (a,b) in sortedB:
        sharedEdges.add((a,b))
print(sharedEdges)

For the above code, I'm pretty sure the issue is within the if statement; if I used the same list input for both, I still get an empty output.

If I try to use the intersection function, I get the error: TypeError: unhashable type: 'list'

sharedEdges = set(sortedAlt) & set(sortedB)
sharedEdges = list(set(sortedAlt)-set(sortedAlt))
print(sharedEdges)