Detailed explanation of three methods of string concatenation in Python and their efficiency and applicable scenarios-Python Tutorial-php.cn

Detailed explanation of three methods of string concatenation in Python and their efficiency and applicable scenarios

高洛峰

Release： 2017-02-11 13:00:26

Original

1607 people have browsed it

This article mainly introduces the three methods of string connection in Python, their efficiency, and detailed explanations of applicable scenarios. It has certain reference value and interested friends can refer to it.

There are generally three ways to connect Python strings:

Method 1: Connect directly through the plus (+) operator

website = &#39;python&#39; + &#39;tab&#39; + &#39;.com&#39;

Copy after login

Method 2: join method

listStr = [&#39;python&#39;, &#39;tab&#39;, &#39;.com&#39;] 
website = &#39;&#39;.join(listStr)

Copy after login

Method 3: Replace

website = &#39;%s%s%s&#39; % (&#39;python&#39;, &#39;tab&#39;, &#39;.com&#39;)

Copy after login

Let’s talk about three more methods The difference

Method 1 is simple and direct to use, but many people on the Internet say that this method is inefficient

The reason why using + for string concatenation in python is inefficient , because strings in python are immutable types. When using + to connect two strings, a new string will be generated. To generate a new string, you need to apply for memory again. When there are many strings that are continuously added ( a+b+c+d+e+f+...), low efficiency is inevitable

Method 2 is slightly complicated to use, but it is efficient when connecting multiple characters, and it will only happen once Memory application. And if you are connecting characters in a list, this method must be the first choice

Method 3: String formatting, this method is very commonly used, and I also recommend this method

The following experiments are used to illustrate the efficiency of string concatenation.

Comparison object: plus connection VS join connection

Python version: python2.7

System environment: CentOS

Experiment 1:

# -*- coding: utf-8 -*-

from time import time

def method1():

  t = time()

  for i in xrange(100000):

    s = &#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;

  print time() - t

def method2():

  t = time()

  for i in xrange(100000):

    s = &#39;&#39;.join([&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;])

  print time() -t

method1()

method2()

Copy after login

Result:

0.641695976257

0.341440916061

Experiment 2:

# -*- coding: utf-8 -*-

from time import time

def method1():

  t = time()

  for i in xrange(100000):

    s = &#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;+&#39;pythontab&#39;

  print time() - t

def method2():

  t = time()

  for i in xrange(100000):

    s = &#39;&#39;.join([&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;,&#39;pythontab&#39;])

  print time() -t

method1()

method2()

Copy after login

Result:

0.0265691280365

0.0522091388702

The above two experiments produced completely different results. The only difference between the two experiments is the number of string connections.

Conclusion: The low efficiency of plus sign connection occurs when multiple string connections are performed continuously. If the number of connections is small, the efficiency of plus sign connection is higher than that of join connection

The above is the entire content of this article. I hope it will be helpful to everyone's learning. I also hope that everyone will support the PHP Chinese website.

For more detailed explanations of the three methods of string connection in python and their efficiency and applicable scenarios, please pay attention to the PHP Chinese website!