assign the reference of an object to the variable

#!/usr/bin/python

l = ['a', 'b', 'c', 'd']

l2 = l

print(id(l), id(l2)) # l and l2 have same id

l2[1] = 't' # change both l and l2

print(l, l2)
			

constructs a new compound object, then inserts references of the elements in the original object into it

# all elements are immutable elements, shallow copy and deep copy have the same effect
 
import copy

l = ['a', 'b', 'c', 'd']
 
l2 = copy.copy(l) # shallow copy
 
print(id(l), id(l2)) # l and l2 have different id
 
l2[1] = 't' # not change l
 
print(l, l2)
			

# have mutable elements, shallow copy and deep copy are not same
 
import copy

l = ['a', 'b', ['ab', 'ba']]
 
l2 = copy.copy(l) # shallow copy
 
print(id(l), id(l2)) # l and l2 have different id
 
l2[2][1] = 't' # change both l and l2
 
print(l, l2)
			

constructs a new compound object, then inserts copies of the elements of the original objects into it

# have object elements, shallow copy and deep copy are not same

import copy

l = ['a', 'b', ['ab', 'ba']]
 
l2 = copy.deepcopy(l) # deep copy
 
print(id(l), id(l2)) # l and l2 have different id
 
l2[2][1] = 't' # not change l
 
print(l, l2)
			

import copy

def info(l, l2):
    print('id: ', id(l), id(l2))
    print(l, l2)

l = [1, 2, 3, [4, 5]]

# copy from both shallow copy and deep copy have different id
 
# Slicing, shallow copy
l2 = l[:]

l2[3][0] = 10 # changed both l and l2
info(l, l2)
 
# list, shallow copy
l2 = list(l)

l2[3][0] = 100 # changed both l and l2
info(l, l2)
 
# copy.copy(), shallow copy
l2 = copy.copy(l)

l2[3][0] = 1 # changed both l and l2
info(l, l2)
 
# copy.deepcopy(), deep copy
l2 = copy.deepcopy(l)

l2[3][0] = 1000 # change l2, not l
info(l, l2)
			

import copy

def info(l, l2):
    print('id: ', id(l), id(l2))
    print(l, l2)

# copy from both shallow copy and deep copy have different id

# Shallow copy
d = {'Name':'Lin', 'List':[1, 2, 3, 4]}
d2 = d.copy()

d2['List'][1] = 10 # change both d and d2
info(d, d2)

# Deep copy
d2 = copy.deepcopy(d)

d2['List'][1] = 10 # change d2, not d
info(d, d2)
			

import copy

def info(i, i2):
    print('id: ', id(i), id(i2))
    print(i, i2)

# for immutable elements, shallow copy and deep copy are same
i = (1, 2, (3, 4))
 
i2 = copy.copy(i) # i and i2 have same ids
info(i, i2)
 
i2 = copy.deepcopy(i) # i and i2 have same ids
info(i, i2)
 
# containing mutable elements
 
# Shallow copy
l = (1, 2, [3, 4])
 
l2 = copy.copy(l) # i and i2 have the same ids
info(l, l2)
 
l2 = l+() # i and i2 have the same ids
info(l, l2)
 
# deep copy
l2 = copy.deepcopy(l) # l and l2 have the different ids
info(l, l2)
			

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