![]() ![]() The concept was also alluded to in the preliminary report for the IAL (ALGOL 58) in that the syntax allowed one or more indices of an array element (or, for that matter, of a procedure call) to be omitted when used as an actual parameter. Slicing as a language feature probably started with FORTRAN (1957), more as a consequence of non-existent type and range checking than by design. ![]() The concept of slicing was surely known even before the invention of compilers. In 1-based schemes, -1 generally would indicate the second-to-last item, while in a 0-based system, it would mean the very last item. If the array abstraction does not support true negative indices (as for example the arrays of Ada and Pascal do), then negative indices for the bounds of the slice for a given dimension are sometimes used to specify an offset from the end of the array in that dimension. For languages that allow arbitrary lower bounds for indices, like Pascal, the dope vector needs 1 3 d entries. For languages like C, where the indices always start at zero, the dope vector of an array with d indices has at least 1 2 d parameters. This technique also allows immediate array transposition, index reversal, subsampling, etc. General array slicing can be implemented (whether or not built into the language) by referencing every array through a dope vector or descriptor – a record that contains the address of the first array element, and then the range of each index and the corresponding coefficient in the indexing formula. However, since the range can be specified at run-time, type-checked languages may require an explicit (compile-time) notation to actually eliminate the trivial indices. This feature can be used, for example, to extract one-dimensional slices (vectors: in 3D, rows, columns, and tubes ) or two-dimensional slices (rectangular matrices) from a three-dimensional array. Reducing the range of any index to a single value effectively eliminates that index. In programming languages that use a 0-based indexing scheme, the slice would be from index 2 to 5. Thus, if we have a vector containing elements (2, 5, 7, 3, 8, 6, 4, 1), and we want to create an array slice from the 3rd to the 6th items, we get (7, 3, 8, 6). Also depending on the language, the elements of the new array may be aliased to (i.e., share memory with) those of the original array.įor "one-dimensional" (single-indexed) arrays – vectors, sequence, strings etc. – the most common slicing operation is extraction of zero or more consecutive elements. In computer programming, array slicing is an operation that extracts a subset of elements from an array and packages them as another array, possibly in a different dimension from the original.Ĭommon examples of array slicing are extracting a substring from a string of characters, the " ell" in "h ello", extracting a row or column from a two-dimensional array, or extracting a vector from a matrix.ĭepending on the programming language, an array slice can be made out of non-consecutive elements. For other uses of slicing, see Slicing (disambiguation). To take trailing and leading whitespaces into consideration, then add a sign to the RegEx string to match one or more consecutive whitespaces as a single group.Īlso, append the keyword r to the RegEx string to ensure that Python processes the escape sequences appropriately.This article is about the data structure operation. \s is a collation of every type of whitespace, including the ones mentioned above ( \n, \t, \r, \f).įor example, declare a string and perform re.split() to split them into an array of substrings. The RegEx keyword that represents whitespace is \s. The re.split() function accepts two main parameters, a RegEx string and the string to perform the split function. ![]() Although, note that the re.split() is slower compared to the built-in split() method performance-wise. The Python RegEx (Regular Expressions) module re also has a pre-defined split() function that we can use in place of the built-in split() method. ![]() Use re.split() to Split a String in Python Considering these factors, you don’t have to worry about explicitly trimming every whitespace before executing the function. ![]()
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