Python List Assignment

Python List Assignment-31
Python provides a wide range of ways to modify lists.A single value in a list can be replaced by indexing and simple assignment: The number of elements inserted need not be equal to the number replaced. You can insert multiple elements in place of a single element—just use a slice that denotes only one element: Note: Technically, it isn’t quite correct to say a list must be concatenated with another list.loop is a way to do operations many times, a list is a way to store many values.

Python provides a wide range of ways to modify lists.

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All the usual syntax regarding indices and slicing applies to sublists as well: .

An individual element in a sublist does not count as an element of the parent list(s).

We create a list by putting values inside square brackets and separating the values with commas: Data which can be modified in place is called mutable, while data which cannot be modified is called immutable. This does not mean that variables with string or number values are constants, but when we want to change the value of a string or number variable, we can only replace the old value with a completely new value.

Lists and arrays, on the other hand, are mutable: we can modify them after they have been created.

If we make a list and (attempt to) copy it then modify in place, we can cause all sorts of trouble: Subsets of lists and strings can be accessed by specifying ranges of values in brackets, similar to how we accessed ranges of positions in a Num Py array.

This is commonly referred to as “slicing” the list/string.You should consider both of these aspects when writing your code.While modifying in place, it is useful to remember that Python treats lists in a slightly counter-intuitive way.Lists are defined in Python by enclosing a comma-separated sequence of objects in square brackets ( Each of these features is examined in more detail below. (You will see a Python data type that is not ordered in the next tutorial on dictionaries.) Lists that have the same elements in a different order are not the same: Individual elements in a list can be accessed using an index in square brackets.This is exactly analogous to accessing individual characters in a string. Consider the following list: It’s not an accident that strings and lists behave so similarly.But what if we want to take a subset of entries that aren’t next to each other in the sequence?You can achieve this by providing a third argument to the range within the brackets, called the Notice that the slice taken begins with the first entry in the range, followed by entries taken at equally-spaced intervals (the steps) thereafter.But you can operate on a list literal as well: You have seen that an element in a list can be any sort of object. A list can contain sublists, which in turn can contain sublists themselves, and so on to arbitrary depth.Consider this (admittedly contrived) example: There is no limit, short of the extent of your computer’s memory, to the depth or complexity with which lists can be nested in this way.Would your solution work regardless of whether you knew beforehand the length of the string or list (e.g.if you wanted to apply the solution to a set of lists of different lengths)?


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