my_foods = ['pizza','falafel','carrot cake']
friend_foods = my_foods[:]

print(my_foods)
print(friend_foods)
>>>['pizza', 'falafel', 'carrot cake']
>>>['pizza', 'falafel', 'carrot cake']
my_foods = ['pizza','falafel','carrot cake']
# friend_foods和my_foods指向同一个列表
friend_foods = my_foods
my_foods.append('cannoli')
friend_foods.append('ice cream')
print(my_foods)
print(friend_foods)
>>>['pizza', 'falafel', 'carrot cake', 'cannoli', 'ice cream']
>>>['pizza', 'falafel', 'carrot cake', 'cannoli', 'ice cream']