Increment element in a list and append to new list

I need to increment a single item in a list (x) and append the result to a new list (y).

This works fine on a single variable as the below example:

y = []

for x in range(100):
    x += 1
    print(x)
    y.append(x)

print(y)

but when I try to do it within an existing list only the last iteration is being appended to the new list, example:

x = [1,2,3,4,5]
y = []
for i in range(100):
    x[1] = x[1] + 1
    print(x)
    y.append(x)

print(y)

The desired result is that the 2nd element of list y[1] is incremented by range(100) in the resulting list y, like so:

[[1, 3, 3, 4, 5], [1, 4, 3, 4, 5], [1, 5, 3, 4, 5], ... [1, 101, 3, 4, 5], [1, 102, 3, 4, 5]

Solution

You are adding the same instance of x to the list each time, so the resulting values will all be the same.

You could add a copy of x instead:

x = [1,2,3,4,5]
y = []
for i in range(100):
    x[1] = x[1] + 1
    print(x)
    y.append(x.copy())

print(y)

Obviously there are more efficient ways to do this, but this is a way that is easy to understand.

Output:

[[1, 3, 3, 4, 5], [1, 4, 3, 4, 5], ... [1, 100, 3, 4, 5], [1, 101, 3, 4, 5], [1, 102, 3, 4, 5]]