![]() ![]() How many ways can you make change for a $100 dollar bill? You have three $20 dollar bills, five $10 dollar bills, two $5 dollar bills, and five $1 dollar bills. If you get a NameError: name 'itertools' is not defined or a NameError: name 'it' is not defined exception when running one of the examples in this tutorial you’ll need to import the itertools module first. All itertools methods in code examples are prefaced with it. Note: From this point forward, the line import itertools as it will not be included at the beginning of examples. Taking a naive approach, you might write something like this: For example, if inputs = and n = 2, your function should return. For simplicity, assume that the length of the input list is divisible by n. Given a list of values inputs and a positive integer n, write a function that splits inputs into groups of length n. To see this, consider the following problem: There are two main reasons why such an “iterator algebra” is useful: improved memory efficiency (via lazy evaluation) and faster execuction time. So, in a way, if you have ever used zip() or map() in Python 3, you have already been using itertools! In Python 3, izip() and imap() have been removed from itertools and replaced the zip() and map() built-ins. To return an iterator, the izip() and imap() functions of itertools must be used. ![]() Historical Note: In Python 2, the built-in zip() and map() functions do not return an iterator, but rather a list. This is what is meant by the functions in itertools forming an “iterator algebra.” itertools is best viewed as a collection of building blocks that can be combined to form specialized “data pipelines” like the one in the example above.
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