From zero to learn Python's Hello World

Simple ' Hello world! '

Python command line

Assuming you have already installed Python, enter it on the Linux command line:

The code is as follows:

$python

Will go directly to Python. Then, at the command line prompt >>> later enter:

The code is as follows:

>>>print (' Hello world! ')

You can see it and then output it on the screen:

The code is as follows:

Hello world!

Print is a commonly used function that outputs strings in parentheses.

(in Python 2.x, print can also be a keyword that can be written as print ' Hello world! ', but this won't work in 3.x)
Write a small program

Another way to use Python is to write a Python program. Write a file with a. py ending in a text editor, such as hello.py

Write the following in hello.py, and Save:

The code is as follows:

Print (' Hello world! ')

Exit the text editor and enter it at the command line:

The code is as follows:

$python hello.py

To run hello.py. You can see that Python then outputs

The code is as follows:

Hello world!

Script

We can also change the Python program hello.py to an executable script that executes directly:

The code is as follows:

#!/usr/bin/env python

Print (' Hello world! ')

You need to modify the permissions of the above program to be executable:

The code is as follows:

chmod 755 hello.py

Then, in the command line, enter

The code is as follows:

./hello.py

You can run it directly.
Summarize

Print

Command-line mode: Run Python, enter commands at the command line, and execute.

Program mode: Write a Python program and run it.

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