如果元素相同，则为二维数组

Question

I have list of lists looks like

a=[[1,2],[2,1],[2,3]]

I would like to check if the fırst elements of sublist are same, if they are same I would like to put them a new list.

I tried

for x in a:
    for y in x:
        if y in x:

I could not find what to write after that. My output is that new lists like

a1=[[2,3,1],[1,2]] 

Thank you

Answer 1

I'll go for dictionary.

a = [[1,2],[2,1],[2,3]]

d = {}
for x in a:
    head = x[0]
    if head in d.keys():
        d[head].extend(x[1:])
    else:
        d[head] = x[1:]

result = [[key] + d[key] for key in d.keys()]

Answer 2

Try this:

a=[[2,2],[2,1],[2,3]]
myList=[x[0] for x in a]
print(all(y==myList[0] for y in myList))

If same then True else False