What are the built-in functions of python?

The so-called built-in functions are functions that are automatically loaded in Python and can be used at any time. Built-in function, which means we don't have to import the module in order to use the function. You don't have to do anything for Python to recognize built-in functions.

In the process of learning Python, there are several important functions:

1.help() function

2.dir() function

3.input() and raw_input() function

4.print() function

5.type() function

help function:

There are two types of parameters for the help() function:

If you pass a string as a parameter, it will automatically search for modules, methods, etc. named after this string.

If an object is passed in, help for the type of the object will be displayed.

For example, if you enter help('print'), it will look for modules, classes, etc. named 'print'. If it cannot find it, you will see a prompt message. Print is a reserved word in Python, the same as pass and return, not an object, so help(print) will also report an error.

For example:

1 >>>help(’sys’)       #会列出sys模块的帮助 
2 >>>a = [1,2,3]
3 >>>help(a)       #会显示list的帮助
4 >>>help(a.append) #会显示list的append方法的帮助

dir function:

dir() function returns a list of properties and methods of any object, including module objects and functions Object, string object, list object, dictionary object, etc. Although finding and importing modules is relatively easy, remembering what each module contains is not. You don't want to always have to look at the source code to find out. Fortunately, Python provides a way to inspect the contents of modules (and other objects) using the built-in dir() function. When you provide a module name to dir(), it returns a list of properties defined by the module. If no arguments are provided, it returns a list of properties defined in the current module. The dir() function works on all object types, including strings, integers, lists, tuples, dictionaries, functions, custom classes, class instances, and class methods.

For example:

1 >>>dir()       #列出当前模块的属性列表
2 ['__builtins__', '__doc__', '__name__', '__package__']    #当前模块的属性列表

input and raw_input functions:

The input() and raw_input() functions are both used to read user input , the difference is that the input() function expects the user to enter a valid expression, while the raw_input() function wraps the user's input into a string.

For example:

1 >>>input(’please input:’)     
2 please input:2+3
3 5       #结果是5，而非'2+3'，因为Python认为你输入的是表达式
4 >>>raw_input(’please input:’)     
5 please input:2+3
6 '2+3'   #结果是'2+3'，因为Python认为你输入的是原生字符串

print function:
Print was used as a Python statement before the Python3 version, and in Python3 print was used as a function. .

For example:

1 >>>print ’hello world’
2 >>>print('hello world')

type function:

The type() function returns the data type of any object. Possible data types are listed in the types module, which is useful for helper functions that handle multiple data types. It does this by returning a type object, which can be compared to the types defined in the types module.

For example:

1 >>>type(’hello’)     
2     #字符串数据类型str
3 >>>type(10)     
4     #整数数据类型int

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