what is the difference between a list and a dictionary in python?
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A list is an ordered sequence of objects, whereas dictionaries are unordered sets. However, the main difference is that items in dictionaries are accessed via keys and not via their position. ... The values of a dictionary can be any type of Python data. So, dictionaries are unordered key-value-pairs.
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In python, a dictionary can only hold a single value for a given key. However, if you use a relevant data type for that value, you should be able to save multiple values for a single key. Option 1: Use a tuple to represent the value of the key.
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Lists are mutable objects which means you can modify a list object after it has been created. Tuples, on the other hand, are immutable objects which means you can't modify a tuple object after it's been created. Both Mutability and Immutability have their own advantages and disadvantages.
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Yes, it is a hash mapping or hash table. You can read a description of python's dict implementation, as written by Tim Peters, here. You can read more about hash tables or check how it has been implemented in python and why it is implemented that way.
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In Python, list is akin to arrays in other scripting languages(Ruby, JavaScript, PHP). It allows you to store an enumerated set of items in one place and access an item by its position – index. ... Each item in the list has a value(color name) and an index(its position in the list). Python uses zero-based indexing.
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Unlike strings that contain only characters, list and tuples can contain any type of objects. Lists and tuples are like arrays. ... Lists are mutables so they can be extended or reduced at will. Sets are mutable unordered sequence of unique elements whereas frozensets are immutable sets.
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A set is a collection which is unordered and unindexed, and doesnt allow duplicates. In Python, sets are written with curly brackets. A list is a collection which is ordered and changeable. In Python lists are written with square brackets.
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In Dictionary, key must be unique. Duplicate keys are not allowed if you try to use duplicate key then compiler will throw an exception. In Dictionary, you can only store same types of elements.
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Because dict is the name of a built-in type in Python you are seeing what appears to be a strange error message, but in reality it is not. ... All types are objects in Python. Thus you are actually trying to index into the type object. This is why the error message says that the "'type' object is not subscriptable."
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It provides a high-performance multidimensional array object, and tools for working with these arrays. A numpy array is a grid of values, all of the same type, and is indexed by a tuple of nonnegative integers. ... A list is the Python equivalent of an array, but is resizeable and can contain elements of different types.
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The difference to List now is that List is untyped and therefore no type checks at all are performed, which ultimately leads to certain warnings and can lead to weird runtime behavior. While Java knows that List<Object> is a list that might contain anything, it doesn't know that about a List .
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Lets dive deeper into the details of it… Since everything in Python is an Object, every variable holds an object instance. ... Objects of built-in types like (int, float, bool, str, tuple, unicode) are immutable. Objects of built-in types like (list, set, dict) are mutable. Custom classes are generally mutable.
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The main difference between List and IList in C#.NET is that List is a class that represents a list of objects which can be accessed by index while IList is an interface that represents a collection of objects which can be accessed by index. ... Overall, List is a concrete type that implements the IList interface.
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And while most of the data types we've worked with in introductory Python are immutable (including integers, floats, strings, Booleans, and tuples), lists and dictionaries are mutable. That means a global list or dictionary can be changed even when it's used inside of a function, just like we saw in the examples above.
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A list holds different data such as Numeric, Character, logical, etc. Vector stores elements of the same type or converts implicitly. Lists are recursive, whereas vector is not. The vector is one-dimensional, whereas the list is a multidimensional object.
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arrays and dictionaries both store collections of data, but differ by how they are accessed. Items in an array are accessed by position (often a number) and hence have an order. Items in a dictionary are accessed by key and are unordered. Sets are groups of items, unordered with duplicates removed.
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A list is an ordered collection of values. The values that make up a list are called its elements, or its items. We will use the term element or item to mean the same thing. Lists are similar to strings, which are ordered collections of characters, except that the elements of a list can be of any type.