Python List copy() Method
Copies the list shallowly
copy() method returns the Shallow copy of the specified list.
# Create a copy of list 'L' L = ['red', 'green', 'blue'] X = L.copy() print(X) # Prints ['red', 'green', 'blue']
copy() vs Assignment statement
Assignment statement does not copy objects. For example,
old_List = ['red', 'green', 'blue'] new_List = old_List new_List = 'xx' print(old_List) # Prints ['xx', 'green', 'blue'] print(new_List) # Prints ['xx', 'green', 'blue']
When you execute
new_List = old_List, you don’t actually have two lists. The assignment just makes the two variables point to the one list in memory.
So, when you change new_List, old_List is also modified. If you want to change one copy without changing the other, use
old_List = ['red', 'green', 'blue'] new_List = old_List.copy() new_List = 'xx' print(old_List) # Prints ['red', 'green', 'blue'] print(new_List) # Prints ['xx', 'green', 'blue']
Assigning a slice of the entire list to a variable is equivalent to
L = ['red', 'green', 'blue'] X = L[:] print(X) # Prints ['red', 'green', 'blue']
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There are two sides to machine learning:
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- Theoretical Machine Learning: This is about math and abstraction and idealized scenarios and limits and beauty and informing what is possible. It is a whole lot neater and cleaner and removed from the mess of reality.
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