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Python Built-in Class Functions
dict()
  Parameters
  Remarks
frozenset()
  Parameters
  Remarks
list()
  Parameters
  Remarks
set()
  Parameters
  Remarks
tuple()
  Parameters
  Remarks
 Source and Reference

Python Built-in Class Functions

The Python interpreter has some built-in class functions.

dict()

class dict(**kwarg) class dict(mapping, **kwarg) class dict(iterable, **kwarg)

Parameters

dict()to return a new dictionary. **kwargto specify the keyword arguments to be returned from mappingto specify the mapping object to be returned from iterableto specify the iterable to be returned from

Remarks

  • Return a new dictionary initialized from an optional positional argument and a possibly empty set of keyword arguments. If no positional argument is given, an empty dictionary is created. If a positional argument is given and it is a mapping object, a dictionary is created with the same key-value pairs as the mapping object. Otherwise, the positional argument must be an iterable object. Each item in the iterable must itself be an iterable with exactly two objects. The first object of each item becomes a key in the new dictionary, and the second object the corresponding value. If a key occurs more than once, the last value for that key becomes the corresponding value in the new dictionary. If keyword arguments are given, the keyword arguments and their values are added to the dictionary created from the positional argument. If a key being added is already present, the value from the keyword argument replaces the value from the positional argument. Providing keyword arguments as in the first example only works for keys that are valid Python identifiers. Otherwise, any valid keys can be used.

frozenset()

class frozenset([iterable])

Parameters

frozensetto return a frozenset object [iterable]optional, to specify an iterable to be returned from

Remarks

  • A set object is an unordered collection of distinct hashable objects. Common uses include membership testing, removing duplicates from a sequence, and computing mathematical operations such as intersection, union, difference, and symmetric difference. (For other containers see the built-in dict, list, and tuple classes, and the collections module.) Like other collections, sets support x in set, len(set), and for x in set. Being an unordered collection, sets do not record element position or order of insertion. Accordingly, sets do not support indexing, slicing, or other sequence-like behavior. There are currently two built-in set types, set and frozenset. The set type is mutable — the contents can be changed using methods like add() and remove(). Since it is mutable, it has no hash value and cannot be used as either a dictionary key or as an element of another set. The frozenset type is immutable and hashable — its contents cannot be altered after it is created; it can therefore be used as a dictionary key or as an element of another set. Non-empty sets (not frozensets) can be created by placing a comma-separated list of elements within braces

list()

class list([iterable])

Parameters

list()to return a list [iterable]optional, to specify an iterable to be returned from

Remarks

  • Lists are mutable sequences, typically used to store collections of homogeneous items (where the precise degree of similarity will vary by application). class list([iterable]) Lists may be constructed in several ways: Using a pair of square brackets to denote the empty list: [] Using square brackets, separating items with commas: [a], [a, b, c] Using a list comprehension: [x for x in iterable] Using the type constructor: list() or list(iterable) The constructor builds a list whose items are the same and in the same order as iterable’s items. iterable may be either a sequence, a container that supports iteration, or an iterator object. If iterable is already a list, a copy is made and returned, similar to iterable[:]. For example, list('abc') returns ['a', 'b', 'c'] and list( (1, 2, 3) ) returns [1, 2, 3]. If no argument is given, the constructor creates a new empty list, []. Many other operations also produce lists, including the sorted() built-in.

set()

class set([iterable])

Parameters

set()to return a set [iterable]optional, to specify an iterable to be returned from

Remarks

  • A set object is an unordered collection of distinct hashable objects. Common uses include membership testing, removing duplicates from a sequence, and computing mathematical operations such as intersection, union, difference, and symmetric difference. (For other containers see the built-in dict, list, and tuple classes, and the collections module.) Like other collections, sets support x in set, len(set), and for x in set. Being an unordered collection, sets do not record element position or order of insertion. Accordingly, sets do not support indexing, slicing, or other sequence-like behavior. There are currently two built-in set types, set and frozenset. The set type is mutable — the contents can be changed using methods like add() and remove(). Since it is mutable, it has no hash value and cannot be used as either a dictionary key or as an element of another set. The frozenset type is immutable and hashable — its contents cannot be altered after it is created; it can therefore be used as a dictionary key or as an element of another set. Non-empty sets (not frozensets) can be created by placing a comma-separated list of elements within braces

tuple()

class tuple([iterable])

Parameters

tuple()to return a tuple [iterable]optional, to specify an iterable to be returned from

Remarks

  • Tuples are immutable sequences, typically used to store collections of heterogeneous data (such as the 2-tuples produced by the enumerate() built-in). Tuples are also used for cases where an immutable sequence of homogeneous data is needed (such as allowing storage in a set or dict instance). Tuples may be constructed in a number of ways: Using a pair of parentheses to denote the empty tuple: () Using a trailing comma for a singleton tuple: a, or (a,) Separating items with commas: a, b, c or (a, b, c) Using the tuple() built-in: tuple() or tuple(iterable) The constructor builds a tuple whose items are the same and in the same order as iterable’s items. iterable may be either a sequence, a container that supports iteration, or an iterator object. If iterable is already a tuple, it is returned unchanged. For example, tuple('abc') returns ('a', 'b', 'c') and tuple( [1, 2, 3] ) returns (1, 2, 3). If no argument is given, the constructor creates a new empty tuple, (). Note that it is actually the comma which makes a tuple, not the parentheses. The parentheses are optional, except in the empty tuple case, or when they are needed to avoid syntactic ambiguity. For example, f(a, b, c) is a function call with three arguments, while f((a, b, c)) is a function call with a 3-tuple as the sole argument.

Source and Reference


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