The itertools python module implements some basic building blocks for iterators. As they say, “they form an iterator algebra”. I was expecting, but I could not find a succinctly way of doing the following iteration using the module. Given a list of ordered real numbers, for example … return …
Tag: iterator
Simplest way to get the first n elements of an iterator
How can I get the first n elements of an iterator (generator) in the simplest way? Is there something simpler than, e. g. I can’t think of a nicer way, but maybe there is? Maybe a functional form? Answer Use itertools.islice(): This will yield the next 3 elements from it, then stop.
Easiest way to include a stop parameter in enumerate python?
Ss there a simple way to iterate over an iterable object that allows the specification of an end point, say -1, as well as the start point in enumerate. e.g. So if my object has a length of 10, what is the simplest way to to get it to start iterating at index 2 and stop iterating at index 9?
What is the difference between chain and chain.from_iterable in itertools?
I could not find any valid example on the internet where I can see the difference between them and why to choose one over the other. Answer The first takes 0 or more arguments, each an iterable, the second one takes one argument which is expected to produce the iterables: but iterables can be any iterator tha…
custom dict that allows delete during iteration
UPDATED based on Lennart Regebro’s answer Suppose you iterate through a dictionary, and sometimes need to delete an element. The following is very efficient: The only overhead here is building the list of keys to remove; unless it grows large compared to the dictionary size, it’s not an issue. How…
Is there a Java equivalent of Python’s ‘enumerate’ function?
In Python, the enumerate function allows you to iterate over a sequence of (index, value) pairs. For example: Is there any way of doing this in Java? Answer For collections that implement the List interface, you can call the listIterator() method to get a ListIterator. The iterator has (amongst others) two me…
How to convert an iterable to a stream?
If I’ve got an iterable containing strings, is there a simple way to turn it into a stream? I want to do something like this: Answer Here’s my streaming iterator an experimental branch of urllib3 supporting streaming chunked request via iterables: Source with context: https://github.com/shazow/url…
Is enumerate in python lazy?
I’d like to know what happens when I pass the result of a generator function to python’s enumerate(). Example: Is the enumeration iterated lazily, or does it slurp everything into the <enumerate object> first? I’m 99.999% sure it’s lazy, so can I treat it exactly the same as the …
Get the first item from an iterable that matches a condition
I would like to get the first item from a list matching a condition. It’s important that the resulting method not process the entire list, which could be quite large. For example, the following function is adequate: This function could be used something like this: However, I can’t think of a good …
When is not a good time to use python generators?
This is rather the inverse of What can you use Python generator functions for?: python generators, generator expressions, and the itertools module are some of my favorite features of python these days. They’re especially useful when setting up chains of operations to perform on a big pile of data–…