如何用相同的 x 为 y 创建两个点？

Question

I'm trying to make a python code to create "double points", where one single value for x would assume two values for y for any situation. Here is a example of data:

1;5
2;-2
3;4
4;10.4
5;6

where first column(x), is just an index for position of the data (y).

Plotting this data into x and y, would form a straight line.

The result I would like to have is:

1;5
1;-2
2;-2
2;4
3;4
3;10.4
4;10.4
4;6
5;6

This would generate a rectangular chart. The value of x has its respective value of y, but that same value of x also has the value of y for its "x + 1" , and so for the rest of the data.

I'm trying to do something like this, however unsuccessful:

l = [5, -2, 4, 10.4, 6]
m = []
i = 0
i = i+1
for i in range(len(l)):
    m.append(l[i])
    if i < len(l)-1:
        m.append([l[i][0], l[i+1][1]])
    print('{}, {}\n' .format(i, m[i]))

The error that appears is 'int' object has no attribute '__getitem__'

I am new to python and this is part of my studies, so if anyone can help me and can explain where I am going wrong, I would be grateful.

Ps the x column is not part of the data, is just an index (like time for example). And the data (y column) can be negative, floats... all of types of numbers

Answer 1

can be done using list comprehension like below

from itertools import chain
ls = [5, -2, 4, 10.4, 6]
list(chain(*([(i,v)]*2 for i, v in enumerate(ls))))[1:]

Answer 2

Try matching the items on each list depending on their index. Eg with list.index(item) :

y=[5, -2, 4, 10.4, 6]
x=[i for i in range(len(y)+1) if i!=0]

for item in x:
    for i in y:
        if x.index(item) == y.index(i):
            print('%s;%s' %(item, i))
        if x.index(item)==y.index(i) -1:
            print('%s;%s' %(item, i))