Python on String invariance

>>> ' abc ' + ' Def '

' ABCdef '

Python allocates space for ' abc ' and ' Def ' respectively, and Python automatically allocates space for the new string ' abcdef ' When the connection operation is made

>>>s = ' abc '

>>>s = s + ' def '

>>>s

' ABCdef '

In the example above, it seems that we have assigned ' ABC ' to S and added ' Def ' to the end of S. This looks like the string seems to be mutable.

In fact, in the "s + ' def '" Operation, a new string was created, and then the new object was assigned to S, the original character

The string ' abc ' was released.

We can use the ID () function to demonstrate

>>>s = ' abc '

>>>id (s)

4455368904

>>>s + = ' def '

>>>id (s)

4456241552

The identities are different before and after the obvious changes.

Python on String invariance