Accessing values of dict inside list with indexes

Question

I had a requirement in one of my codes to access values from a list of dictionaries that I initialized with default values. My object looked like this:

>>> lengths = [{"max_len":0,"eq_len":True}] * 7
>>> print(lengths)

[{'max_len': 0, 'eq_len': True}, {'max_len': 0, 'eq_len': True}, {'max_len': 0, 'eq_len': True}, {'max_len': 0, 'eq_len': True}, {'max_len': 0, 'eq_len': True}, {'max_len': 0, 'eq_len': True}, {'max_len': 0, 'eq_len': True}]

Surprisingly, when I'm trying to update any one of the values in this lengths object directly, all the other objects are also getting updated. For ex:

>>> col_lengths[0]["max_len"] = 10
>>> print(col_lengths)

[{'max_len': 10, 'eq_len': True}, {'max_len': 10, 'eq_len': True}, {'max_len': 10, 'eq_len': True}, {'max_len': 10, 'eq_len': True}, {'max_len': 10, 'eq_len': True}, {'max_len': 10, 'eq_len': True}, {'max_len': 10, 'eq_len': True}]

>>> col_lengths[4]["eq_len"] =  False     
>>> print(col_lengths)

[{'max_len': 10, 'eq_len': False}, {'max_len': 10, 'eq_len': False}, {'max_len': 10, 'eq_len': False}, {'max_len': 10, 'eq_len': False}, {'max_len': 10, 'eq_len': False}, {'max_len': 10, 'eq_len': False}, {'max_len': 10, 'eq_len': False}]

Looks like this behavior is unexpected. Or am I doing something wrong? Can someone please help me with this?

It seems like when you create the list of dictionaries using *7, you are having them reference the same object. Try looping through a list and append it n number of times. That should help in creating a unique object instead of reusing the same object in the list. — mindless-overflow, Jan 18 '20 at 21:41

Accessing values of dict inside list with indexes

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