In this article, we've briefly looked at how to declare arrays in Python, how to access values in an array, and also how to cut – or slice – a part of an array using a colon and square brackets.
It means "all elements of the sequence but the last". In the context of f.readline()[:-1] it means "I'm pretty sure that line ends with a newline and I want to strip it".
For negative indexing, to display the 1st element to last element in steps of 1 in reverse order, we use the [::-1]. The [::-1] reverses the order. In a similar way, we can slice strings like this. Remember, negative number for step means "in reverse order". Let us now see examples ? Use the [::-1] to reverse the order of a string in Python ?
It is done using the slicing operator [:]. The operator takes two arguments separated by a colon. The first argument specifies the index of the element where the slice starts and the second argument specifies the index of the element where the slice ends.
So [::-1] means from 1st element to last element in steps of 1 in reverse order. If you have [start:stop] it's the same as step=1. So [:-1] it means all but last. again it's the last element exclusive. It's the same as [:-1:] or [0:-1:1]. If you have only start, it returns one element given by the index start. Thus [-1] means last element.
Python operators are special symbols or keywords used to perform specific operations. Depending on the operator, we can perform arithmetic calculations, assign values to variables, compare two or more values, use logical decision-making in our programs, and more.
Discover the meaning and uses of [:] inPython, a powerful slicing operator for lists, strings, and more. Learn how to effectively apply it to extract, copy, or manipulate data in your Python programs.
A [-1] is used for negative indexes and helps select items in reverse order in a given list. It signifies the beginning of the list from the end of the reverse order.
The double colon (::) operator in Python, also referred to as slice notation or the slicing operator, provides an elegant and flexible way to slice and extract subsequences from ordered sequences like lists, strings, tuples, arrays etc.
Python’s [::-1] notation is a slice that’s employed quite often, especially when it comes to reversing sequences like lists or strings. To someone new to Python, this syntax may appear somewhat enigmatic.
