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Python | Categorize tuple values into dictionary value list
• Last Updated : 26 Jul, 2019

Sometimes, while working with Python, we might face a problem in which we have data in form of list of tuples, and what we intend is, to categorize them into dictionary with a value list of tuples. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using `setdefault()` + loop
This task can easily be performed using `setdefault()`. In this, we just take key and value pair of tuple by iteration and `setdafault()` is used to assign value to corresponding key of dictionary.

 `# Python3 code to demonstrate working of``# Categorize tuple values into dictionary value list``# Using setdefault() + loop`` ` `# Initialize list of tuples``test_list ``=` `[(``1``, ``3``), (``1``, ``4``), (``2``, ``3``), (``3``, ``2``), (``5``, ``3``), (``6``, ``4``)]`` ` `# printing original list``print``(``"The original list : "` `+`  `str``(test_list))`` ` `# Using setdefault() + loop``# Categorize tuple values into dictionary value list``res ``=` `{}``for` `i, j ``in` `test_list:``     ``res.setdefault(j, []).append(i)`` ` `# printing result ``print``(``"The dictionary converted from tuple list : "` `+` `str``(res))`
Output :

The original list : [(1, 3), (1, 4), (2, 3), (3, 2), (5, 3), (6, 4)]
The dictionary converted from tuple list : {2: , 3: [1, 2, 5], 4: [1, 6]}

Method #2 : Using `dict()` + list comprehension + `frozenset()`
The combination of above methods can be used to perform this particular task. In this, the logical computations are done in comprehension with the help of `frozenset()` and the container is converted to dictionary using `dict()`.

 `# Python3 code to demonstrate working of``# Categorize tuple values into dictionary value list``# Using dict() + list comprehension + frozenset()`` ` `# Initialize list of tuples``test_list ``=` `[(``1``, ``3``), (``1``, ``4``), (``2``, ``3``), (``3``, ``2``), (``5``, ``3``), (``6``, ``4``)]`` ` `# printing original list``print``(``"The original list : "` `+`  `str``(test_list))`` ` `# Using dict() + list comprehension + frozenset()``# Categorize tuple values into dictionary value list``res ``=` `dict``((key, [i[``0``] ``for` `i ``in` `test_list ``if` `i[``1``] ``=``=` `key])``             ``for` `key ``in` `frozenset``(j[``1``] ``for` `j ``in` `test_list))`` ` `# printing result ``print``(``"The dictionary converted from tuple list : "` `+` `str``(res))`
Output :

The original list : [(1, 3), (1, 4), (2, 3), (3, 2), (5, 3), (6, 4)]
The dictionary converted from tuple list : {2: , 3: [1, 2, 5], 4: [1, 6]}

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