Functional Python Programming

Using reversed() to change the order

There are times when we need a sequence reversed. Python offers us two approaches to this: the reversed() function and slices with reversed indices.

For an example, consider performing a base conversion to hexadecimal or binary. The following is a simple conversion function:

def digits(x, b):
    if x == 0: return
    yield x % b
    for d in to_base(x//b, b):
        yield d

This function uses a recursion to yield the digits from the least significant to the most significant. The value of x%b will be the least significant digits of x in the base b.

We can formalize it as following:

In many cases, we'd prefer the digits to be yielded ...