I have my array is : Li = [[1,2,3],[4,5,6],[7,8,9]] how can check if value exist in an array . Example

if 5 exist in Li return Li[1][1] so I can change the value of that item by making Li[1][1]= 
"X"

CodePudding user response：

If your nested list is always a 2D matrix of numbers, then you can find the indices fairly easily:

def find_indices(nested_list, value):
    
    for i, inner_list in enumerate(nested_list):
        for j, item in enumerate(inner_list):
            if item == value:
                return (i,j) # return a tuple containing the indices

Li = [[1,2,3],[4,5,6],[7,8,9]]
print(find_indices(Li, 5))

This example uses the enumerate function in Python, which gives you the index and item inside of an iterable object.

CodePudding user response：

To be honest it is hard to understand what u really want, or if u urself even know that. Here is some input that might help u:

from typing import List


def is_value_in_list_of_lists(
    value_to_check: int, list_of_lists: List[List[int]]
) -> bool:
    for v in list_of_lists:  # v::List[int]
        if value_to_check in v:
            return True
    return False

def replace_all_occurrences_of_value_in_list_of_lists(
    value_to_check: int, value_to_replace_with: str, list_of_lists: List[List[int]]
) -> List[List[int]]:
    if is_value_in_list_of_lists(value_to_check, list_of_lists):
        modified_list_of_lists = []

        for v in list_of_lists:  # v::List[int]
            if value_to_check not in v:
                modified_list_of_lists.append(v)
            else:
                # modify list
                v_modified = []

                for val in v:  # val::int
                    if val == value_to_check:
                        v_modified.append(value_to_replace_with)
                    else:
                        v_modified.append(val)
                modified_list_of_lists.append(v_modified)
        return modified_list_of_lists
    else:
        return list_of_lists

if __name__ == "__main__":
    lists = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
    # True
    print(is_value_in_list_of_lists(5, lists))
    # [[1, 2, 3], [4, 'X', 6], [7, 8, 9]]
    print(replace_all_occurrences_of_value_in_list_of_lists(5, "X", lists))
    # oneliner
    # [[1, 2, 3], [4, 'X', 6], [7, 8, 9]]
    print(list([*map(lambda x: "X" if x == 5 else x, y)] for y in lists))