![]() If items is not None and items is not None: Mylist = list(itertools.izip_longest(a1,b1,c1,d1)) ![]() When iterating through unequal length lists using itertools Short answer for py2.6+: use "map(None, alist, blist)" See below for a discussion of how to use the longest list instead: Re:#8, unequal list length: the result is truncated to the shorter list. In order to use zip to iterate over two lists - Do the two lists have to be the same size? What happens if the sizes are unequal? Thanks. I do not know the number of such sets in advance. I have set of n set, each with different number of elements I wanted to find all possible combinations of n elements, one from each set. Jeremy, Thanks for the example, It is very helpful. Thanks for the zip example, I grok it now. It was great to talk to you today and I hope I can talk to you again soon. I had heard of itertools but have not really used it. Thanks for the tip and the clear example and demonstration of the performance benefit. Where a = b = xrange(100000) and delta(f(x)) denotes the runtime in seconds of f(x). #2 Jeremy Lewis commented on : > def foo(): Yields the exact same result as above, but is faster and uses less memory. from itertools import izip, countįor i, a, b in izip(count(), alist, blist): The zip object offers some interesting functionality (for instance, it’s faster to iterate over it than the list), but we often need to convert it to list.If you're working with last lists and/or memory is a concern, using the itertools module is an even better option. We’ve established that the zip() function returns a zip object - this behavior is similar to how map() operates. Essentially, it governs how the iterable object should be iterated over.Ĭonverting a zip() Object into a List (and Using Indices) It also remembers its position during iteration. An iterator is an object that represents a stream of data it returns the data one element at a time.An Iterable is an object that we can loop over (e.g.A good example is the loop - it works with each individual item until the whole set of items is exhausted. Iteration is a general computer science term it refers to performing an action to a set of elements, one element at a time. ![]() We’ll reuse the explanation that we produced in the article about the map() function: These concepts are an integral part of computer science and general, so it’s important to drive their meaning home. ![]() You may have noticed that terms like iteration, iterable, and iterator appear frequently. The workaround involves converting the zip object into a list - we’ll learn how to do it in the next section. The caveat associated with zip objects is that they aren’t subscriptable, meaning it’s impossible, among other things, to navigate through it using indices. list) in the sections below, but you do need to keep this little detail in mind. We’ learn how to convert it into other data types (e.g. Although it may seem that we get a list upon calling this function, it actually returns a special data type called zip object. One important thing to know is what the zip() function returns. As we can see, there are only three triplets even though the lists uppercase and lowercase have five and four elements, respectively. ![]()
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