An example Analysis of shallow replication in Clippers, Java and Python
This article introduces the relevant knowledge of "shallow copy example Analysis in Clearing, Java, Python". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!
01
The question of shallow copy and deep copy of the object is often asked in the interview, whether it is Clippers, Java, or Python. Today, we take Python as an example to illustrate the problem of shallow replication.
02
Start with copy () of List
Let's start with something simple, as follows:
Monkeys = ['jone','yone','mary']
Wukongs = monkeys.copy ()
Print (wukongs)
> ['jone',' yone', 'mary']
We successfully cloned wukongs.
At this point, it's just a copy, and you can't see what a shallow copy is.
03
Next, let's look at shallow replication.
We add a group of animals to the monkeys population, as follows, and then copy the monkeys.
Monkeys.append (['nuzha','honghaier'])
Print (monkeys)
# > ['jone',' yone', 'mary', [' nuzha', 'honghaier']]
Print (wukongs)
# > ['jone',' yone', 'mary']
# copy mokeys to wukongs again
Wukongs = monkeys.copy ()
Print (wukongs)
# >
Print wukongs at this time, and you can see:
['jone',' yone', 'mary', [' nuzha', 'honghaier']]
This is not surprising at all, and then there is the moment to witness miracles:
Wukongs [- 1] .append ('houzi')
Print (wukongs)
Print (monkeys)
When we add an animal: houzi from the last element of wukongs, which is also a list, we only add an animal to wukongs. It's not surprising to print it at this time, but print monkeys and find that it also has houzi.
['jone',' yone', 'mary', [' nuzha', 'honghaier',' houzi']] ['jone',' yone', 'mary', [' nuzha', 'honghaier',' houzi']]
This is shallow copy, when an element in a list is an object, such as list, tuple, dict and self-built classes, if you execute copy (), the element only copies the pointer value and does not copy its memory recursively. Therefore, it will cause the above phenomenon, because it is two references to the same memory address.
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