Hello, I hope you are following this course from the beginning. With today's tutorial, we are heading towards more and more interesting data structures in python.
Links to previous tutorials are available at the bottom of this article
ChainMap is a data type in Python. It is a container that encapsulates many dictionaries into one unit. The combined dictionaries contain keys and values in specific sequences. The best use of ChainMap is to search through multiple dictionaries at a time and get proper key-value pair. It is often much faster than creating a new dictionary and running multiple update() calls.
Are you confused? Don’t worry, let's implement to get a better idea about this.
Creating a ChainMap
First of all, we have to import ChainMap from the ‘collections’ module:
from collections import ChainMapNow let's create a ChainMap:
d1 = {'day1': 'Mon', 'day2': 'Tue'}
d2 = {'day3': 'Wed', 'day1': 'Thu'}c_m = ChainMap(d1, d2)print(c_m)#OUTPUT
ChainMap({'day1': 'Mon', 'day2': 'Tue'}, {'day3': 'Wed', 'day1': 'Thu'})
In the above example, we created two dictionaries and then stored those in one ChainMap.
Accessing
ChainMap supports all usual dictionary methods. In it has a map() method which is used to display keys with corresponding values of all the dictionaries in ChainMap in a stored state. It is a user updatable list mapping.
Let’s see how to use it:
print(c_m.maps) #here we used maps method on c_m and printed it#OUTPUT
[{'day1': 'Mon', 'day2': 'Tue'}, {'day3': 'Wed', 'day1': 'Thu'}]
Accessing Keys and Values
We can access the list of keys and values using the key() and value() methods in ChainMap.
ks = list(c_m.keys()) # List of keys
print(ks)#OUTPUT
['day3', 'day1', 'day2']vs = list(c_m.values()) #List of values
print(vs)#OUTPUT
['Wed', 'Mon', 'Tue']#Printing all values
for key, value in c_m.items():
print(f"key: {key}, value: {value}")#OUTPUT:
key: day3, value: Wed
key: day1, value: Mon
key: day2, value: Tue
Here in the above example of accessing the list of keys and values, you should notice that in the list of keys, a duplicate key is removed, and in the list of values value of that duplicate key is removed.
Updating
When elements in the dictionary are updated then ChainMap is also instantly updated.
d2['day3'] = 'Sun'print(c_m.maps)#OUTPUT
[{'day1': 'Mon', 'day2': 'Tue'}, {'day3': 'Sun', 'day1': 'Thu'}]
That should be enough for this tutorial I hope you enjoyed this tutorial. See you tomorrow, bye!!
Lectures
Lecture 1: https://medium.com/@saifmdco/data-structures-with-python-introduction-4dadeffa2215
Lecture 2: https://medium.com/@saifmdco/data-structures-with-python-arrays-c498518bf7fd
Lecture 3: https://medium.com/@saifmdco/data-structures-in-python-lists-653a3ad103ab
Lecture 4: https://medium.com/@saifmdco/data-structures-in-python-tuples-3c350640cd9a
Lecture 5: https://medium.com/@saifmdco/data-structures-in-python-dictionary-fad27ffdda8b
Lecture 6: https://medium.com/@saifmdco/data-structures-in-python-2d-array-6bc0154aa717
Lecture 7: https://medium.com/@saifmdco/data-structures-in-python-matrix-22adba5aa597
Lecture 8: https://medium.com/@saifmdco/data-structures-in-python-sets-92d5445e97e8
Lecture 9: https://medium.com/@saifmdco/data-structures-in-python-chainmap-fca2a9d47249
Lecture 10: https://medium.com/@saifmdco/data-structures-in-python-linkedlist-50f2118c659e
Lecture 11: https://medium.com/@saifmdco/data-structures-in-python-stack-6bf182d63581
Lecture 12: https://medium.com/@saifmdco/data-structures-in-python-queue-6361d3dcff0
Lecture 13: https://medium.com/@saifmdco/data-structures-in-python-dequeue-1a585e269a55
Lecture 14: https://medium.com/@saifmdco/data-structures-in-python-custom-stack-b7b9173b4eae
Lecture 15: https://medium.com/@saifmdco/data-structures-in-python-hash-table-39be784eefc1
Lecture 16: https://medium.com/@saifmdco/data-structures-in-python-doubly-linked-list-fe698d74756c
