# Python | Convert list of tuple into dictionary

• Last Updated : 26 Aug, 2019

Given a list containing all the element and second list of tuple depicting the relation between indices, the task is to output a dictionary showing the relation of every element from the first list to every other element in the list.
These type of problems are often encountered in Coding competition.
Below are some ways to achieve the above task.

```Input:
indices = ['x','y','z','w','t','r']
relation =[('x', 'y'), ('x', 'z'), ('x', 'w'), ('y', 'z'), ('y', 'w'), ('z', 'w')]
Output:
{'x': ['y', 'z', 'w'], 'y': ['x', 'z', 'w'], 'z': ['x', 'y', 'w'],
'w': ['x', 'y', 'z'], 't': [], 'r': []}
```

Method #1: Using iteration is the easiest way to solve any task

 `#Python code to convert list of tuple into dictionary showing ``#relation of every element from first list to every other element in the list.`` ` `#List initialization``indices ``=` `[``'x'``,``'y'``,``'z'``,``'w'``,``'t'``,``'r'``]``relation ``=``[(``'x'``, ``'y'``), (``'x'``, ``'z'``), (``'x'``, ``'w'``), (``'y'``, ``'z'``), (``'y'``, ``'w'``), (``'z'``, ``'w'``)]`` ` `#dictionary initialization``Output ``=` `{}`` ` `#Iteration ``for` `elem ``in` `indices:``     ``temp``=` `[]``     ``for` `rel ``in` `relation:``          ``if` `elem ``in` `rel:``               ``if` `elem ``=``=` `rel[``0``]:``                    ``temp.append(rel[``1``])``               ``else``:``                    ``temp.append(rel[``0``])``      ` `     ``Output[elem] ``=` `temp``     ``temp ``=` `[]`` ` `print``(``"Initial list of tuple is :"``)``print``(relation)``print``(``"Converted dictionary of list :"``)``print``(Output)`
```Output :
Initial list of tuple is :
[('x', 'y'), ('x', 'z'), ('x', 'w'), ('y', 'z'), ('y', 'w'), ('z', 'w')]
Converted dictionary of list :
{'w': ['x', 'y', 'z'], 'r': [], 'x': ['y', 'z', 'w'], 't': [],
'y': ['x', 'z', 'w'], 'z': ['x', 'y', 'w']}
```

Method #2: Using networkx is the most simplest and shortest
way to convert list of tuple into dictionary

 `#Python code to convert list of tuple into dictionary showing ``#relation of every element from first list to every other element in the list.`` ` `#Importing``import` `networkx as nx `` ` `#List initialization``indices ``=` `[``'x'``,``'y'``,``'z'``,``'w'``,``'t'``,``'r'``]``relation ``=``[(``'x'``, ``'y'``), (``'x'``, ``'z'``), (``'x'``, ``'w'``), (``'y'``, ``'z'``), (``'y'``, ``'w'``), (``'z'``, ``'w'``)]`` ` `#dictionary initialization``Output ``=` `{}`` ` `#Using networkx to solve ``temp``=``nx.Graph(relation)``temp.add_nodes_from(indices)``Output ``=` `nx.to_dict_of_lists(temp)`` ` `#Printing``print``(``"Initial list of tuple is :"``)``print``(relation)``print``(``"Converted dictionary of list :"``)``print``(Output)`
```Output :
Initial list of tuple is :
[('x', 'y'), ('x', 'z'), ('x', 'w'), ('y', 'z'), ('y', 'w'), ('z', 'w')]
Converted dictionary of list :
{'w': ['x', 'y', 'z'], 'r': [], 'x': ['y', 'z', 'w'], 't': [],
'y': ['x', 'z', 'w'], 'z': ['x', 'y', 'w']}
```

Method #3: Using itertools and groupby is another way to convert list of tuple into dictionary.

 `#Python code to convert list of tuple into dictionary showing ``#relation of every element from first list to every other element in the list.`` ` `#Importing``from` `itertools ``import` `groupby``from` `operator ``import` `itemgetter`` ` `#List initialization``indices ``=` `[``'x'``,``'y'``,``'z'``,``'w'``,``'t'``,``'r'``]``relation ``=``[(``'x'``, ``'y'``), (``'x'``, ``'z'``), (``'x'``, ``'w'``), (``'y'``, ``'z'``), (``'y'``, ``'w'``), (``'z'``, ``'w'``)]`` ` `#Using itertools.groupby and maps``edge ``=` `relation ``+` `[``tuple``(``reversed``(pair)) ``for` `pair ``in` `relation]``st ``=` `itemgetter(``0``)``end ``=` `itemgetter(``1``)``groups ``=` `groupby(``sorted``(edge), key``=``st)``mapping ``=` `{vertex: ``list``(``map``(end, edges)) ``for` `vertex, edges ``in` `groups}``from` `collections ``import` `defaultdict`` ` `#Output list``Output ``=` `defaultdict(``list``, mapping)``Output ``=` `dict``(mapping)``Output.update({vertex: [] ``for` `vertex ``in` `indices ``if` `vertex ``not` `in` `mapping})`` ` `#Printing``print``(``"Initial list of tuple is :"``)``print``(relation)``print``(``"Converted dictionary of list :"``)``print``(Output)`
```Output :
Initial list of tuple is :
[('x', 'y'), ('x', 'z'), ('x', 'w'), ('y', 'z'), ('y', 'w'), ('z', 'w')]
Converted dictionary of list :
{'w': ['x', 'y', 'z'], 'r': [], 'x': ['y', 'z', 'w'], 't': [],
'y': ['x', 'z', 'w'], 'z': ['x', 'y', 'w']}
```

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