How to set the default parameters of Python functions
We know that if a parameter is not specified when calling a function, the Python interpreter will throw an exception. In order to solve this problem, Python allows setting default values for parameters, that is, when defining a function, directly specify a default value for the formal parameters. In this case, even if no parameter is passed to a formal parameter with a default value when the function is called, the parameter can directly use the default value set when the function is defined.
Python defines a function with default value parameters. The syntax format is as follows:
def 函数名(...,形参名,形参名=默认值): 代码块
Note that when using this format to define a function, the formal parameters with default values must be specified in all default values. value parameter at the end, otherwise a syntax error will occur.
The following program demonstrates how to define and call a function with default parameters:
#str1没有默认参数,str2有默认参数 def dis_str(str1,str2 = "http://c.biancheng.net/python/"): print("str1:",str1) print("str2:",str2) dis_str("http://c.biancheng.net/shell/") dis_str("http://c.biancheng.net/java/","http://c.biancheng.net/golang/")
The running result is:
str1: http://c.biancheng. net/shell/
str2: http://c.biancheng.net/python/
str1: http://c.biancheng.net/java/
str2: http://c.biancheng .net/golang/
In the above program, the dis_str() function has 2 parameters, the second of which has a default parameter. This means that when calling the dis_str() function, we can pass in only 1 parameter, which will be passed to the str1 parameter, and str2 will use the default parameters, as shown in line 6 of the program.
Of course, when calling the dis_str() function, you can also pass values to all parameters (as shown in line 7 of the code). At this time, even if str2 has a default value, it will give priority to the parameters passed to it. new value.
At the same time, combined with keyword parameters, the following three ways of calling the dis_str() function are also possible:
dis_str(str1 = "http://c.biancheng.net/shell/") dis_str("http://c.biancheng.net/java/",str2 = "http://c.biancheng.net/golang/") dis_str(str1 = "http://c.biancheng.net/java/",str2 = "http://c.biancheng.net/golang/")
Again, when defining a function with default value parameters, there are parameters with default values. Must come after all parameters without default values. Therefore, the function defined in the following example is incorrect:
#语法错误 def dis_str(str1="http://c.biancheng.net/python/",str2,str3): pass
Obviously, str1 has a default value, while str2 and str3 do not have default values, so str1 must be located after str2 and str3.
Some readers may ask, for your own custom functions, you can easily know which parameters have default values, but if you use the built-in functions provided by Python, or functions provided by other third parties, how do you know which parameters? Is there a default value?
In Pyhton, you can use "function name.__defaults__" to view the current value of the function's default value parameter, and its return value is a tuple. Take the dis_str() function in this section as an example. Based on it, execute the following code:
print(dis_str.__defaults__)
The program execution result is:
('http://c. biancheng.net/python/',)
The above is the detailed content of How to set the default parameters of Python functions. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics



VS Code can run on Windows 8, but the experience may not be great. First make sure the system has been updated to the latest patch, then download the VS Code installation package that matches the system architecture and install it as prompted. After installation, be aware that some extensions may be incompatible with Windows 8 and need to look for alternative extensions or use newer Windows systems in a virtual machine. Install the necessary extensions to check whether they work properly. Although VS Code is feasible on Windows 8, it is recommended to upgrade to a newer Windows system for a better development experience and security.

In VS Code, you can run the program in the terminal through the following steps: Prepare the code and open the integrated terminal to ensure that the code directory is consistent with the terminal working directory. Select the run command according to the programming language (such as Python's python your_file_name.py) to check whether it runs successfully and resolve errors. Use the debugger to improve debugging efficiency.

VS Code can be used to write Python and provides many features that make it an ideal tool for developing Python applications. It allows users to: install Python extensions to get functions such as code completion, syntax highlighting, and debugging. Use the debugger to track code step by step, find and fix errors. Integrate Git for version control. Use code formatting tools to maintain code consistency. Use the Linting tool to spot potential problems ahead of time.

VS Code extensions pose malicious risks, such as hiding malicious code, exploiting vulnerabilities, and masturbating as legitimate extensions. Methods to identify malicious extensions include: checking publishers, reading comments, checking code, and installing with caution. Security measures also include: security awareness, good habits, regular updates and antivirus software.

Python excels in automation, scripting, and task management. 1) Automation: File backup is realized through standard libraries such as os and shutil. 2) Script writing: Use the psutil library to monitor system resources. 3) Task management: Use the schedule library to schedule tasks. Python's ease of use and rich library support makes it the preferred tool in these areas.

VS Code is the full name Visual Studio Code, which is a free and open source cross-platform code editor and development environment developed by Microsoft. It supports a wide range of programming languages and provides syntax highlighting, code automatic completion, code snippets and smart prompts to improve development efficiency. Through a rich extension ecosystem, users can add extensions to specific needs and languages, such as debuggers, code formatting tools, and Git integrations. VS Code also includes an intuitive debugger that helps quickly find and resolve bugs in your code.

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Golang is more suitable for high concurrency tasks, while Python has more advantages in flexibility. 1.Golang efficiently handles concurrency through goroutine and channel. 2. Python relies on threading and asyncio, which is affected by GIL, but provides multiple concurrency methods. The choice should be based on specific needs.
