Write a python program to insertion at the beginning in ordereddict?
View Discussion Show Improve Article Save Article View Discussion Improve Article Save Article Given an ordered dict, write a program to insert items in beginning of ordered dict. Input: original_dict = {'a':1, 'b':2} item to be inserted ('c', 3) Output: {'c':3, 'a':1, 'b':2} Input: original_dict = {'akshat':1, 'manjeet':2} item to be inserted ('nikhil', 3) Output: {'nikhil':3, 'akshat':1, 'manjeet':2} Python3
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In this tutorial, we will learn how to write a program that will insert at the beginning in an OrderedDict using Python. For a given dictionary that is an OrderedDict, we have to insert items at the beginning of the dictionary. In an OrderedDict the order of the insertion of keys is maintained, unlike in a normal dictionary where the order of the keys is not saved. Let us look at the sample input and output of the program. Input: original_dict = {1: 'a', 2: 'b', 3:'c'} item to be inserted (4, 'd') Output: {4: 'd', 1: 'a', 2: 'b', 3: 'c'} To execute this task we can use the following approaches:
Approach 1: Using concatenation operator (+)The concatenation operator (+) works for joining strings and lists in Python. We can convert the values in the dictionary in the list format and then using this operator, we can join the item which has to be inserted, and the given dictionary in a new dictionary, so that the item will be added in the beginning. AlgorithmFollow the algorithm to understand the approach better. Step 1- Import OrderedDict from collections Step 2- Initialise dictionary with items Step 3- Initialise item which has to be inserted Step 4- Declare a dictionary that will store the result Step 5- Use (+) to add the item at the beginning of the dictionary Step 6- Print the new dictionary as the result Python Program 1Look at the program to understand the implementation of the above-mentioned approach. To get the key-value pairs from the dictionary, we have used the items() method which will return all the items present in a dictionary. We have used the list() method to convert the items of the dictionary in list format.
Approach 2: Using move_to_end() methodThe move_to_end() is a method of the OrderedDict subclass. This method can be used to move an existing key to either end of the dictionary. To add the new item in the dictionary, we can use the update() method. This method will add the specified item at the end of the list. AlgorithmFollow the algorithm to understand the approach better. Step 1- Import OrderedDict in the program Step 2- Initialise a dictionary with items Step 3- Use update() to add the new item in the dictionary Step 4- Use move_to_end() to move the inserted item at the beginning Step 5- Print the new dictionary as the result Python Program 2Look at the program to understand the implementation of the above-mentioned approach. The item which has to be inserted at the beginning is first added in the dictionary using update() then it is shifted to the beginning using the move_to_end() where the position is given as last=False.
ConclusionIn this tutorial, we have seen two different approaches for inserting an item at the beginning of an OrderedDict. We have also seen what an OrderedDict is and how we can use different built-in methods to execute the task. What is an OrderedDict in Python?Python's OrderedDict is a dict subclass that preserves the order in which key-value pairs, commonly known as items, are inserted into the dictionary. When you iterate over an OrderedDict object, items are traversed in the original order. If you update the value of an existing key, then the order remains unchanged.
How do I create an OrderedDict?OrderedDict is part of python collections module. We can create an empty OrderedDict and add items to it. If we create an OrderedDict by passing a dict argument, then the ordering may be lost because dict doesn't maintain the insertion order. If an item is overwritten in the OrderedDict, it's position is maintained.
How is an OrderedDict implemented in Python?Under the hood, OrderedDict is implemented with the help of the doubly-linked list data structure. This is so that the order of the OrderedDict is retained.
How do you create an empty OrderedDict in Python?“generate an empty ordereddict in python” Code Answer. from collections import OrderedDict.. d = OrderedDict(). d['a'] = 1.. d['b'] = 2.. d['c'] = 3.. for key, value in d. items():. |