# Python – Convert List to key-value list by prefix grouping

• Last Updated : 01 Aug, 2020

Given a list, convert it to consecutive key-value lists, grouping by prefix.

Input : test_list = [“GFG-1”, 4, 6, “GFG-2”, 3, “GFG-3”, 9, 2], temp = “GF”
Output : {‘GFG-1’: [4, 6], ‘GFG-2’: , ‘GFG-3’: [9, 2]}
Explanation : All grouped till next prefix.

Input : test_list = [“MRK-1”, 4, 6, “MRK-2”, 3, “MRK-3”, 9, 2], temp = “MR”
Output : {‘MRK-1’: [4, 6], ‘MRK-2’: , ‘MRK-3’: [9, 2]}
Explanation : All grouped till next prefix, “MR”.

Method : Using groupby() + startswith() + lambda

The combination of above functions can be used to solve this problem. In this, we employ grouping of all elements by prefix using groupby() and lambda functions assists in performing segregation of prefix for grouping.

## Python3

 `# Python3 code to demonstrate working of ``# Convert List to key-value list by prefic grouping``# Using groupby() + startswith() + lambda``from` `itertools ``import` `groupby`` ` `# initializing list``test_list ``=` `[``"GFG-1"``, ``4``, ``6``, ``7``, ``"GFG-2"``, ``2``, ``3``, ``"GFG-3"``, ``9``, ``2``, ``4``, ``6``]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# initializing prefix ``temp ``=` `"GFG"`` ` `res ``=` `{}``# extracting result from grouped by prefix``for` `key, val ``in` `groupby(test_list, ``lambda` `ele: ``str``(ele).startswith(temp)):``     ` `    ``# checking for existing key ``    ``if` `key:``        ``k ``=` `next``(val)``    ``else``:``        ``res[k] ``=` `list``(val)``         ` `# printing result ``print``(``"The constructed dictionary : "` `+` `str``(res))`
Output
```The original list : ['GFG-1', 4, 6, 7, 'GFG-2', 2, 3, 'GFG-3', 9, 2, 4, 6]
The constructed dictionary : {'GFG-1': [4, 6, 7], 'GFG-2': [2, 3], 'GFG-3': [9, 2, 4, 6]}
```
My Personal Notes arrow_drop_up