Functional Python Programming

Chapter 8

Function Name Arguments Results

dotproduct (vec1, vec2) This is the essential definition of a dot

product. Multiply two vectors and find the

sum of the result.

flatten (listOfLists) This flattens one level of nesting. This chains

the various lists together into a single list.

repeatfunc (func,

times=None,

*args)

This calls to func repeatedly with specified

arguments.

pairwise (iterable): s -> (s0,s1), (s1,s2), (s2, s3).

grouper (iterable, n,

fillvalue=None)

Collect data into fixed length chunks or

blocks.

roundrobin (*iterables) roundrobin('ABC', 'D', 'EF') -->

A D

E B F C

partition (pred,

iterable)

This uses a predicate to partition entries into

False entries and True entries.

unique_

everseen

(iterable,

key=None)

This lists unique elements, preserving order.

Remembers all elements ever seen. unique_

everseen('AAAABBBCCDAABBB') -

-> A B C D.

unique_

justseen

(iterable,

key=None)

This lists unique elements, preserving order.

Remembers only the element just seen.

unique_justseen('AAAABBBCCDAABBB')

• -> A B C D A B.
  iter_except (func,
  exception,
  first=None)

Call a function repeatedly until an exception

is raised. This can be used to iterate until

KeyError or IndexError.

Summary

In this chapter, we've looked at a number of functions in the itertools module.
This library module provides a number of functions that help us to work with
iterators in sophisticated ways.

We've looked at the infinite iterators; these repeat without terminating. These include
the count(), cycle(), and repeat() functions. Since they don't terminate, the
consuming function must determine when to stop accepting values.