Python group list into dictionary
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I want to generate a dictionary from a list of dictionaries, grouping list items by the value of some key, such as: Show So far I've found two ways of doing this. The first simply iterates over the list, create sublists in the dict for each key value and append elements matching these keys to the sublist: And another using I wonder which alternative is the most efficient? Is there any more pythonic/concise or better performing way of achieving this? View Discussion Improve Article Save Article View Discussion Improve Article Save Article Sometimes, while working with data, we can be encountered with a situation in which we have list of list and we need to group it’s 2nd index with the common initial element in lists. Let’s discuss way in which this problem can be solved. Method : Using The defaultdict can be used to initialize the group elements and loop can be used to group the values together and conversion to dictionary can be done using
Output : The original list is : [['Gfg', 1], ['Gfg', 2], ['is', 3], ['best', 4], ['is', 5]]
The grouped dictionary is : {'Gfg': (1, 2), 'best': (4, ), 'is': (3, 5)}
Group List of Dictionary Data by Particular Key in Python can be done using itertools.groupby() method. Itertools.groupby()This method calculates the keys for each element present in iterable. It returns key and iterable of grouped items.
Let’s see the examples: Example 1: Suppose we have list of dictionary of employee and company. INFO = [
{'employee': 'XYZ_1', 'company': 'ABC_1'},
{'employee': 'XYZ_2', 'company': 'ABC_2'},
{'employee': 'XYZ_3', 'company': 'ABC_3'},
{'employee': 'XYZ_4', 'company': 'ABC_3'},
{'employee': 'XYZ_5', 'company': 'ABC_2'},
{'employee': 'XYZ_6', 'company': 'ABC_3'},
{'employee': 'XYZ_7', 'company': 'ABC_1'},
{'employee': 'XYZ_8', 'company': 'ABC_2'},
{'employee': 'XYZ_9', 'company': 'ABC_1'}
]Now we need to display all the data group by the ‘company’ key name. Code: Python3
Output:
Example 2: Suppose we have list of dictionary of student grades and marks. students = [
{'mark': '65','grade': 'C'},
{'mark': '86','grade': 'A'},
{'mark': '73','grade': 'B'},
{'mark': '49','grade': 'D'},
{'mark': '91','grade': 'A'},
{'mark': '79','grade': 'B'}
]Now we need to display all the data group by the ‘grade’ key. Code: Python3
Output: A
{'mark': '86', 'grade': 'A'}
{'mark': '91', 'grade': 'A'}
B
{'mark': '73', 'grade': 'B'}
{'mark': '79', 'grade': 'B'}
C
{'mark': '65', 'grade': 'C'}
D
{'mark': '49', 'grade': 'D'}How to groupby list of dictionary in Python?Group List of Dictionary Data by Particular Key in Python can be done using itertools. groupby() method.
How do I convert a list to a dictionary in Python?Since python dictionary is unordered, the output can be in any order. To convert a list to dictionary, we can use list comprehension and make a key:value pair of consecutive elements. Finally, typecase the list to dict type.
How do you group dictionary using keys?Method : Using sorted() + items() + defaultdict()
The defaultdict() is used to create a dictionary initialized with lists, items() gets the key-value pair and grouping is helped by sorted().
Can we combine dictionaries if so how?You can merge two dictionaries using the | operator. It is a very convenient method to merge dictionaries; however, it is only used in the python 3.9 version or more.
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