ChainMap
A ChainMap encapsulates many dictionaries into a single unit and returns a list of dictionaries.
Syntax:
class collections.ChainMap(dict1, dict2)
Example:
# Python program to demonstrate
# ChainMap
from collections import ChainMap
d1 = {'a': 1, 'b': 2}
d2 = {'c': 3, 'd': 4}
d3 = {'e': 5, 'f': 6}
# Defining the chainmap
c = ChainMap(d1, d2, d3)
print(c)
Output:
ChainMap({'a': 1, 'b': 2}, {'c': 3, 'd': 4}, {'e': 5, 'f': 6})
Accessing Keys and Values from ChainMap
Values from ChainMap can be accessed using the key name. They can also be accessed by using the keys() and values() method.
Example:
# Python program to demonstrate
# ChainMap
from collections import ChainMap
d1 = {'a': 1, 'b': 2}
d2 = {'c': 3, 'd': 4}
d3 = {'e': 5, 'f': 6}
# Defining the chainmap
c = ChainMap(d1, d2, d3)
# Accessing Values using key name
print(c['a'])
# Accessing values using values()
# method
print(c.values())
# Accessing keys using keys()
# method
print(c.keys())
Output:
1
ValuesView(ChainMap({‘a’: 1, ‘b’: 2}, {‘c’: 3, ‘d’: 4}, {‘e’: 5, ‘f’: 6}))
KeysView(ChainMap({‘a’: 1, ‘b’: 2}, {‘c’: 3, ‘d’: 4}, {‘e’: 5, ‘f’: 6}))
Adding new dictionary
A new dictionary can be added by using the new_child() method. The newly added dictionary is added at the beginning of the ChainMap.
Example:
# Python code to demonstrate ChainMap and
# new_child()
import collections
# initializing dictionaries
dic1 = { 'a' : 1, 'b' : 2 }
dic2 = { 'b' : 3, 'c' : 4 }
dic3 = { 'f' : 5 }
# initializing ChainMap
chain = collections.ChainMap(dic1, dic2)
# printing chainMap
print ("All the ChainMap contents are : ")
print (chain)
# using new_child() to add new dictionary
chain1 = chain.new_child(dic3)
# printing chainMap
print ("Displaying new ChainMap : ")
print (chain1)
Output:
All the ChainMap contents are :
ChainMap({'a': 1, 'b': 2}, {'b': 3, 'c': 4})
Displaying new ChainMap :
ChainMap({'f': 5}, {'a': 1, 'b': 2}, {'b': 3, 'c': 4})
Note: For more information, refer ChainMap in Python
Python Collections Module
The collection Module in Python provides different types of containers. A Container is an object that is used to store different objects and provide a way to access the contained objects and iterate over them. Some of the built-in containers are Tuple, List, Dictionary, etc. In this article, we will discuss the different containers provided by the collections module.
Table of Content:
- Counters
- OrderedDict
- DefaultDict
- ChainMap
- NamedTuple
- DeQue
- UserDict
- UserList
- UserString