python - Appending data to lists of multiple elements appends it to all element's lists -


given following sample code:

class parent:     some_list = []  # type: list[int]      def __init__(self, id):         self.id = id  if __name__ == '__main__':     list_of_parents = []  # type: list[parent]      # create 10 parents     in range(10):         list_of_parents.append(parent(i))      # go on each parent , add 10 integers each of lists     i, p in enumerate(list_of_parents):         j in range(10):             list_of_parents[i].some_list.append(1)

after executing code, there list of 10 parent objects, each of them have list 100 entries. (consisting of 10 times integers 0-9), though j elements explicitly added list_of_parents[i].

what's reason this?

it's moses koledoye mentioned. try , see difference:

class parent:      def __init__(self, id):         self.id = id         self.some_list = []# type: list[int]  if __name__ == '__main__':     list_of_parents = []  # type: list[parent]      # create 10 parents     in range(10):         list_of_parents.append(parent(i))      # go on each parent , add 10 integers each of lists     i, p in enumerate(list_of_parents):         j in range(10):             list_of_parents[i].some_list.append(1)             print(list_of_parents[i].some_list)             print("__________")

output:

[1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1] __________ [1, 1] __________ [1, 1, 1] __________ [1, 1, 1, 1] __________ [1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1] __________ [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] __________

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