Python sorted containers | An Introduction

Sorted Containers is an Apache2 licensed sorted collections library, written in pure-Python, and fast as C-extensions. It was created by Grant Jenks and is an open source library. It is a collection of containers that allow us to insert and remove elements very efficiently while maintaining sorted order.

Features:

  • Pure-Python
  • Fully documented
  • Benchmark comparison (alternatives, runtimes, load-factors
  • Performance (often faster than C implementations)
  • Compatible API (nearly identical to popular blist and rbtree modules)
  • Feature-rich (e.g. get the five largest keys in a sorted dict: d.iloc[-5:])
  • Pragmatic design (e.g. SortedSet is a Python set with a SortedList index)

Containers:



  • SortedList
  • SortedDict
  • SortedSet

Installation:

Mac and Linux users can install via pip command:

 sudo pip install sortedcontainers 

SortedList –

Sorted list is a sorted mutable sequence in which the values are maintained in sorted order.

Functions to add and remove elements:

add(value) : A function that takes one element as parameter and inserts it into the list by maintaining sorted order. Runtime Complexity: O(log(n))

update(iterable): A function that takes an iterable as input and updates the SortedList adding all the values from the iterable Runtime complexity: O(k*log(n)).

clear(): Remove all values from sorted list. Runtime complexity: O(n).

discard(value): Remove value from sorted list if it is a member. If value is not a member, do nothing. Runtime complexity: O(log(n)).

Below is the implementation –

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# importing libraries
from sortedcontainers import SortedList, SortedSet, SortedDict
  
# initializing a sorted list with parameters
# it takes an iterable as a parameter.
sorted_list = SortedList([1, 2, 3, 4])
  
# initializing a sorted list using default constructor
sorted_list = SortedList()
  
# inserting values one by one using add()
for i in range(5, 0, -1):
    sorted_list.add(i)
  
# prints the elements in sorted order
print('list after adding 5 elements: ', sorted_list)
  
print('list elements are: ', end = '')
  
# iterating through a sorted list
for i in sorted_list:
    print(i, end = ' ')
print()
  
# removing all elements using clear()
sorted_list.clear()
  
# adding elements using the update() function
elements = [10, 9, 8, 7, 6]
  
sorted_list.update(elements)
  
# prints the updated list in sorted order
print('list after updating: ', sorted_list)
  
# removing a particular element
sorted_list.discard(8)
  
print('list after removing one element: ', sorted_list)
  
# removing all elements
sorted_list.clear()
  
print('list after removing all elements using clear: ', sorted_list)

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Output :


list after adding 5 elements:  SortedList([1, 2, 3, 4, 5], load=1000)

list elements are: 1 2 3 4 5 

list after updating:  SortedList([6, 7, 8, 9, 10], load=1000)

list after removing one element:  SortedList([6, 7, 9, 10], load=1000)

list after removing all elements using clear:  SortedList([], load=1000)

SortedSet –

Sorted set is a sorted mutable set in which values are unique and maintained in sorted order. Sorted set uses a set for set-operations and maintains a sorted list of values. Sorted set values must be hashable and comparable.

Functions to add and remove elements:

add(value) : A function that takes one element as parameter and inserts it into the set by maintaining sorted order. Runtime Complexity: O(log(n))

clear(): Remove all values from sorted set. Runtime complexity: O(n)

discard(value): Remove value from sorted set if it is a member. If value is not a member, do nothing. Runtime complexity: O(log(n))

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# importing libraries
from sortedcontainers import SortedList, SortedSet, SortedDict
  
# initializing a sorted set with parameters
# it takes an iterable as an argument
sorted_set = SortedSet([1, 1, 2, 3, 4])
  
# initializing a sorted set using default constructor
sorted_set = SortedSet()
  
# inserting values one by one
for i in range(5, 0, -1):
    sorted_set.add(i)
  
print('set after adding elements: ', sorted_set)
  
# inserting duplicate value
sorted_set.add(5)
  
print('set after inserting duplicate element: ', sorted_set)
  
# discarding an element
sorted_set.discard(4)
  
print('set after discarding: ', sorted_set)
  
# checking membership using 'in' operator
if(2 in sorted_set):
    print('2 is present')
else:
    print('2 is not present')
  
print('set elements are: ', end = '')
  
# iterating through a sorted set
for i in sorted_set:
    print(i, end = ' ')
print()

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Output :

set after adding elements:  SortedSet([1, 2, 3, 4, 5], key=None, load=1000)

set after inserting duplicate element:  SortedSet([1, 2, 3, 4, 5], key=None, load=1000)

set after discarding:  SortedSet([1, 2, 3, 5], key=None, load=1000)

2 is present

set elements are: 1 2 3 5

SortedDict –

Sorted dict is a sorted mutable mapping in which keys are maintained in sorted order. Sorted dict inherits from dict to store items and maintains a sorted list of keys. Sorted dict keys must be hashable and comparable.

Functions to add and remove elements:

setdefault(key, default = None) : Return value for item identified by key in sorted dict. If key is in the sorted dict then return its value. If key is not in the sorted dict then insert key with value default and return default. Runtime Complexity: O(log(n))

clear(): Remove all values from sorted dict. Runtime complexity: O(n)

get(key, default): Return the value for key if key is in the dictionary, else default.

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# importing libraries
from sortedcontainers import SortedList, SortedSet, SortedDict
  
# initializing a sorted dict with parameters
# it takes a dictionary object as a parameter
sorted_dict = SortedDict({'a': 1, 'b': 2, 'c': 3})
  
# initializing a sorted dict
sorted_dict = SortedDict({'a': 1, 'c': 2, 'b':3})
  
# print the dict
print('sorted dict is: ', sorted_dict)
  
# adding key => value pairs
sorted_dict['d'] = 3
  
print('sorted dict after adding an element: ', sorted_dict)
  
# adding element using setdefault()
sorted_dict.setdefault('e', 4)
  
print('sorted dict after setdefault(): ', sorted_dict)
  
# using the get function
print('using the get function to print the value of a: ', sorted_dict.get('a', 0))
  
# checking membership using 'in' operator
if('a' in sorted_dict):
    print('a is present')
else:
    print('a is not present')
  
print('dict elements are: ', end = '')
  
# iterating over key => value pairs in a dictionary
for key in sorted_dict:
    print('{} -> {}'.format(key, sorted_dict[key]), end = ' ')
print()
  
# removing all elements from the dict
sorted_dict.clear()
  
print('sorted dict after removing all elements: ', sorted_dict)

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Output :

sorted dict is:  SortedDict(None, 1000, {'a': 1, 'b': 3, 'c': 2})

sorted dict after adding an element:  SortedDict(None, 1000, {'a': 1, 'b': 3, 'c': 2, 'd': 3})

sorted dict after setdefault():  SortedDict(None, 1000, {'a': 1, 'b': 3, 'c': 2, 'd': 3, 'e': 4})

using the get function to print the value of a:  1

a is present

dict elements are: a -> 1 b -> 3 c -> 2 d -> 3 e -> 4 

sorted dict after removing all elements:  SortedDict(None, 1000, {})

Reference: http://www.grantjenks.com/docs/sortedcontainers/index.html



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