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Find_symmetric question

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#1

def find_symmetric(my_list):
ret = []
dict = {}
for i in my_list:
if len(i)==2:
dict[i[0]] = i[1]
if i[1] in dict and dict[i[1]] == i[0]:
ret.append(i)

return ret

The above was my solution to Challenge 3 but am getting “list index out of range” errors- could someone suggest why?

#2

Hello, @TL_89,
Your solution for the stated problem statement is almost correct. However, you are only appending one pair inside the ret list. For instance, if i[1] in dict and dict[i[1]] == i[0], it only appends one pair and not the corresponding symmetric pair, i.e., it only appends [3, 4] and misses out the [4, 3] pair and hence throwing an error. Adding this line inside the final if statement resolves the error: 

ret.append([i[1], i[0]])

Final solution then becomes: 

def find_symmetric(my_list):
    ret = []
    dict = {}
    for i in my_list:
        if len(i)==2:
            dict[i[0]] = i[1]
        if i[1] in dict and dict[i[1]] == i[0]:
            ret.append(i)
            ret.append([i[1], i[0]])
    return ret

Hope this answers your query. Feel free to ask any questions if you still have any confusion.