Square brackets
Square brackets are paired punctuation marks used in programming-language syntax to delimit expressions or constructs, including indexing and collection literals.
Statistics Slam Dunk
An extraction operator is syntax that selects a subset of elements from an R vector, matrix, array, list, or data frame.
- How it is used
- Uses indexing to select data-frame columns for calculations and replace invalid vector values before analysis.
- How deep it goes
- Defines extraction operators and demonstrates positional selection, conditional selection, indexed assignment, and validation.
- Examples
- Demonstrates selecting salary and win columns, calculating team summaries, and replacing 227 negative win-share records.
- What you can do after
- Diagnose and correct selected R values while extracting columns for practical NBA data summaries.
Get Programming: Learn to code with Python
Square bracket notation is Python syntax that places an index or slice specification inside brackets to access part of a sequence.
- How it is used
- Accesses elements in lists and characters or substrings in strings.
- How deep it goes
- Defines indexing, negative positions, slicing syntax, and out-of-range errors through short examples and checks.
- Examples
- Uses grocery lists, “Python rules!”, student records, character indexes, and quick-check expressions.
- What you can do after
- Apply it in Python to create lists, retrieve sequence items, slice strings, and recognize invalid list indexes.
Read how Get Programming: Learn to code with Python explains square brackets →
Related concepts
- listuses · A list is an ordered collection of elements arranged in a sequence.
- __getitem__equivalent to · __getitem__ is a Python special method that defines subscription access to an object's elements using square-bracket notation.
- array literaluses · An array literal is source-code syntax that directly specifies the elements of an array.
- dotted notationalternative to · Dotted notation is syntax that uses periods to access or invoke members, qualify names, or represent hierarchical paths.
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