import copy

def main():
    # Unlike arrays, lists are typed only by the
    # elements they contain (not the number of elements).
    # An uninitialized list is empty and has length 0.
    s = []
    print("uninit:", s, s == None, len(s) == 0)

    # To create an empty list with non-zero length, use
    # list multiplication. Here we make a list of
    # strings of length 3 (initially None-valued).
    s = [None] * 3
    print("emp:", s, "len:", len(s), "cap:", len(s))

    # We can set and get just like with arrays.
    s[0] = "a"
    s[1] = "b"
    s[2] = "c"
    print("set:", s)
    print("get:", s[2])

    # len returns the length of the list as expected.
    print("len:", len(s))

    # In addition to these basic operations, lists
    # support several more that make them richer than
    # arrays. One is the append method, which
    # adds one or more new values to the end of the list.
    s.append("d")
    s.extend(["e", "f"])
    print("apd:", s)

    # Lists can also be copied. Here we create a
    # new list c with the same contents as s.
    c = s.copy()
    print("cpy:", c)

    # Lists support a "slice" operator with the syntax
    # list[low:high]. For example, this gets a slice
    # of the elements s[2], s[3], and s[4].
    l = s[2:5]
    print("sl1:", l)

    # This slices up to (but excluding) s[5].
    l = s[:5]
    print("sl2:", l)

    # And this slices up from (and including) s[2].
    l = s[2:]
    print("sl3:", l)

    # We can declare and initialize a variable for list
    # in a single line as well.
    t = ["g", "h", "i"]
    print("dcl:", t)

    # Lists can be compared for equality.
    t2 = ["g", "h", "i"]
    if t == t2:
        print("t == t2")

    # Lists can be composed into multi-dimensional data
    # structures. The length of the inner lists can
    # vary, unlike with multi-dimensional arrays.
    twoD = [[] for _ in range(3)]
    for i in range(3):
        inner_len = i + 1
        twoD[i] = [i + j for j in range(inner_len)]
    print("2d: ", twoD)

if __name__ == "__main__":
    main()