Python string Connection efficiency issues

The connection efficiency of strings has been mentioned in the discussion of Python efficiency, and most recommend using join instead of "+" for string connections

Everything in Python object string object is the C API stringobject.c see Python Source objects file can be found

1. "+". Using the plus sign to connect 2 strings calls the static function String_concat (register pystringobject *a, register pyobject * b), which in this function will open a block of memory that is the size of a+b and then A, b string Copy in, imagine, if it is n strings connected then will open up n-1 times memory, is more resource-intensive

2. For the use of the Join function "". The join ([A, b]) call to the String_join function calculates the length of the list one time to allocate a chunk of memory and then copy it, so the number of times that n strings are connected to open memory is 1 times.

So if there's only 2 connections, the difference is small, but there's a lot of data.

Add something (note) Python differs from the C language when creating variables

1. Integer, Python has a small integer buffer pool that has a range when defining an integer a=3. Then delete this integer using B=3 to find the address of A, B, and then use C = 1000023 to perform the above operation we found 2 number of addresses not the same small integer buffer pool

2. Python defines a string s = "Hello", g = "Hello" after, the address of S,g is the same, C language definition char a[5] = "Hello", char b[5] = "Hello", the string address of A and B is different, indicating that another memory is requested, PY The interned mechanism used by Thon first queries

Python string Connection efficiency issues