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I've got a list that I create a copy of in order to do some manipulations while still keeping the original list. However, when I set copy_list equal to org_list, they become the same thing, and if I change copy_list, org_list changes too. For example:
org_list = ['y', 'c', 'gdp', 'cap'] copy_list = org_list copy_list.append('hum') print(copy_list) print(org_list) returns
['y', 'c', 'gdp', 'cap', 'hum'] ['y', 'c', 'gdp', 'cap', 'hum'] I don't know too much about what is actually going on but it looks like org_list is actually passing itself to copy_list so that they are actually the same thing.
Is there a way to make an independent copy of org_list without doing something clumsy like:
copy_list = [] for i in org_list: copy_list.append(i) I say this because I have the same problem with other types of variables, for example a pandas dataframe.
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“Copying” a list just creates an alias for the same object in memory. To create a completely independent copy of a list, use the copy module's deepcopy() function.
In Python, we use = operator to create a copy of an object. You may think that this creates a new object; it doesn't. It only creates a new variable that shares the reference of the original object. Let's take an example where we create a list named old_list and pass an object reference to new_list using = operator.
A shallow copy constructs a new compound object and then (to the extent possible) inserts references into it to the objects found in the original. A deep copy constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original.
That is because in python setting a variable actually sets a reference to the variable. Almost every person learning python encounters this at some point. The solution is simply to copy the list:
copy_list = org_list[:] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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