Python3 Study notes--001--python HelloWorld

Python uses UTF-8 encoding by default

A python3 version of the HelloWorld code is as follows:

#!/usr/bin/env pythonprint (' Hello world! ')

If this Python script file is named: hello.py, there are two ways to run this script file:

1. Python hello.py

[email protected] python]$ python hello.py Hello world! [Email protected] python]$

2, modify the hello.py permissions,./hello.py

[Email protected] python]$/hello.py Hello world! [Email protected] python]$

The first row, called the Shebang (shell execution) row, specifies which interpreter to use
The shebang line usually has two types of equations:
#!/bin/bin/python
Or
#!/usr/bin/env python
The first form uses the specified interpreter, and the second equation uses the first Python interpreter found in a shell environment

For both python2.x and python3.x, a reliable and viable approach is to use the LN command to create a link to a different name in the/usr/bin/directory. For example, I only created a Python soft link to the PYTHON3 interpreter, and if necessary, you can create a python2 soft link to the Python2 interpreter.

Key elements of Python:

1. Input and output:

First, the output: print ()

After you install Python on windows, you'll see a python 3.4 Docs Server (pydoc-64 bit) in the menu, and you'll see the following page in your browser when you open it:

Where print is the text I entered, the carriage return will see the following:

I feel that the help document looks a little better in this way.

You can see that many of these parameters have default values, which is a good explanation.

Inputs: Input

Input (...) Input ([prompt]), string Read A string from the standard input.  The trailing newline is stripped. If the user hits EOF (unix:ctl-d, Windows:ctl-z+return), raise Eoferror.on Unix, GNU readline is used if enabled.  The prompt string, if given,is printed without a trailing newline before reading.

It is important to note that input returns a string type

An example of using input and print:

#!/usr/bin/env pythonprint (' Hello world! ') Name=input ("Input your Name:") print ("Your name is:" + name)

You can see that declaring a variable in Python is not necessary to indicate its type, which is a bit like JS.

2. int and Str in the built-in type

In Python, the int type is much friendlier than the C language, and we can use a very large number of int types without worrying about overflow

For string types, you can use [] to get a character in a string

However, it is necessary to propose that both int and string types are immutable. However, we can change the type of a data item by using an int (str) that can be str (int).

3. Object references

In Python, you can use the = operator to direct a variable to another variable, a practical example:

[Email protected] python]$/bin/cat hello.py #!/usr/bin/env pythonprint (' Hello world! ')  Name=input ("Input your Name:") var=nameprint ("Your name is:" + var) sex=input ("Input your Sex:") var=sexprint ("Your name is : "+ var" age=input ("Input your Age:") var=int print ("Your-is:", sep= ', end= ') print (VAR) [[Email protected] Pyth  on]$./hello.py Hello world!input your name:xiao dai mayour name Is:xiao dai mainput your sex:nanyour name Is:naninput Your Age:24your age Is:24[[email protected] python]$

You can see that the Var variable refers to a different variable, and the type of the content and value that it points to also changes.

HelloWorld here for the time being.

Python3 Learning Note--001--python HelloWorld