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Python – Character indices Mapping in String List
When it is required to find character indices that map to a string list, a simple iteration, list comprehension and ‘add’ method is used.
Example
Below is a demonstration of the same −
from collections import defaultdict
my_list = ['p y t h o n', 'i s', 'f u n', 't o', 'l e a r n']
print("The list is :")
print(my_list)
my_result = defaultdict(set)
for index, element in enumerate(my_list):
for sub in element.split():
my_result[sub].add(index + 1)
my_result = {key: list(val) for key, val in my_result.items()}
print("The result is :")
print(my_result)Output
The list is :
['p y t h o n', 'i s', 'f u n', 't o', 'l e a r n']
The result is :
{'p': [1], 'y': [1], 't': [1, 4], 'h': [1], 'o': [1, 4], 'n': [1, 3, 5], 'i': [2], 's': [2], 'f': [3], 'u': [3], 'l': [5], 'e': [5], 'a': [5], 'r': [5]}Explanation
The required packages are imported into the environment.
A list is defined and displayed on the console.
An empty dictionary is created using defaultdict.
The list is iterated over using the ‘enumerate’ attribute.
The ‘split’ method is used to split every element, and the ‘add’ method is used to add the element at a specific index in the dictionary.
A dictionary comprehension is used to iterate over elements in the dictionary.
This result is assigned to a variable.
This is the output that is displayed on the console.
Updated on: 08-Sep-2021
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