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Functional Python Programming

Functional Python Programming

By : Steven F. Lott
4 (9)
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Functional Python Programming

Functional Python Programming

4 (9)
By: Steven F. Lott

Overview of this book

This book is for developers who want to use Python to write programs that lean heavily on functional programming design patterns. You should be comfortable with Python programming, but no knowledge of functional programming paradigms is needed.
Table of Contents (18 chapters)
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17
Index

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:

Using reversed() to change the order

In many cases, we'd prefer the digits to be yielded in the reverse order. We can wrap this function with the reversed() function to swap the order of the digits:

def to_base(x, b):
    return reversed(tuple(digits(x, b)))

Note

The reversed() function produces an iterable, but the argument value must be a sequence object. The function then yields the items from that object...

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