Fall in love with the python series-python performance (5): string splicing performance optimization

Strings in python are immutable, and the speed will be slow when splicing, because splicing any immutable sequence will generate a new sequence object

In other words, a lot of intermediate objects will be generated during the splicing process. It will definitely take time to create new objects, and this obviously wastes memory

The optimized way is to use .join() instead

The experiment code is as follows:

import time
import numpy as np

ls=['AA_'+str(i) for i in range(10000000)]
s=""
st=time.time()
for i in ls:
    s+=i

print(time.time()-st)
#print(s)
s=""
st=time.time()
s=s.join(ls)
#print(s)
print(time.time()-st)

operation result:

0.9245333671569824
0.08815383911132812

From the results, it can be seen that the speed of direct splicing will be more than ten times slower, so you need to pay attention when splicing strings.