y = [348, 336, 330, 340, 332, 333, 344, 348, 349, 354, 375, 379, 365, 356, 341, 312, 300, 294, 304, 323].

y = [348, 336, 330, 340, 332, 333, 344, 348, 349, 354, 375, 379, 365, 356, 341, 312, 300, 294, 304, 323]
x = []
for i in range(len(x)):
    x[i] = y[i]
    x.append(x)
print(x)

[]

х = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

y = [348, 336, 330, 340, 332, 333, 344, 348, 349, 354, 375, 379, 365, 356, 341, 312, 300, 294, 304, 323]
x = []
for i in range(len(y)):
    x.append(i)
print(x)

for i in range(len(y))
    x[i] = i;
    x.append(x)
print(x)