In Python you can delete a range within a list by assigning an empty list to a slice. You can also insert the elements of an array into another array using the spread ( …) operator (similar to * in Python): > let arr = Īrray(7) Deleting Ranges > let arr = Īrray // splice() returns a sequence of the removed items.Īrray(4)
The remaining parameters are the items to insert in place of what was removed (and there can be any number of these). However, instead of an end parameter it uses deleteCount: the number of items to remove. This method has a start parameter, which works the same as for slicing.
In JavaScript you splice by calling the array’s splice() method. The official Python documentation just calls it “assigning to a slice”. > arr = Ī Python programmer might not usually use the term “splicing”, since there’s no splice() method. It’s the same syntax as slices, except you add = afterward to replace the slice with a new sequence: > arr It uses start and end parameters, which function the same as start and stop in Python slices: > let arr = Īrray(4) Īrray Splicing in PythonĪs with slices, splicing in Python is done with special syntax. To get a slice of an array, you use the slice() method. Since we’re using a step of 1, we can omit that parameter: > arr = So our slice includes items 1 (“green”) and 2 (“blue”). We start with item 1 (remember, lists are zero-based), and stop right before item 3. If it’s 2, you’re taking every other item. Step: The number of items from one included item to the next. Stop: The index of the first item to *not* include in the slice. Start: The index of the first item to include in the slice. I find that the alliteration makes this easy to remember this way, and slice syntax also uses the same parameters as Python’s range() function. In Python, to get a slice of a list, you use the following syntax: arrayName. The same slicing syntax works in the same way for strings in both languages, but splicing doesn’t: both languages treat strings as immutable. replacing a slice), but possibly just inserting them between existing items.įor both of these features, JavaScript uses built-in methods of the Array class, while Python uses special syntax. Splicing is inserting a sequence of items in an array or list, possibly replacing a given section (i.e. When you use the syntax or method calls provided by the language to get a slice of an array, it’s basically a new array or list that’s shallow copy of that section of the original array/list. Usually it’s a contiguous section (but see the step parameter for an exception to that rule). Slicing and SplicingĪ slice is a section of an array or list. As we’ll see, there are some differences in the syntax used for splicing and splicing, but also a lot of similarities in how slicing and splicing work in the two languages. The differences between the structures they allow, such as that JavaScript arrays can be sparse, while Python’s lists don’t allow this, are beyond the scope of this post. They’re both loosely typed sequences of items, indexed by sequential integers starting at 0, with the ability to add or remove items at any point (in other words, they’re not a fixed length). Lists in Python and arrays in JavaScript are built-in data structures that are used for mostly equivalent things. This is intended as a map between the two languages, rather than a comparison of their strengths and weaknesses. This post covers some of the syntax and parameters for doing array or list slices and splices in Python and JavaScript - in other words, working with sections of lists or arrays, instead of the whole list/array - and some of the similarities and differences between them.
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