View source for Python Programming/Creating Python Programs

← Python Programming/Creating Python Programs

You do not have permission to edit this page, for the following reason:

Your IP address is in a range that has been blocked on all Wikimedia Foundation wikis.

The block was made by ‪Jon Kolbert‬. The reason given is Open proxy/Webhost: See the help page if you are affected .

Start of block: 06:17, 24 January 2024
Expiry of block: 06:17, 24 January 2027

Your current IP address is 3.146.152.76. The blocked range is 3.146.0.0/16.

Please include all above details in any queries you make.

If you believe you were blocked by mistake, you can find additional information and instructions in the Stewards Block Wizard.

You can view and copy the source of this page.

{{Python Programming/Navigation|Self Help|Variables and Strings}}

Welcome to Python! This tutorial will show you how to start writing programs.

Python programs are nothing more than text files, and they may be edited with a standard [[w:Text editor|text editor]] program.<ref>Sometimes, Python programs are distributed in compiled form. We won't have to worry about that for quite a while.</ref> What text editor you use will probably depend on your operating system: any text editor can create Python programs. However, it is easier to use a text editor that includes Python [[w:Syntax highlighting|syntax highlighting]].  


== Hello, World==

The very first program that beginning programmers usually write or learn is the [[w:"Hello, World!" program|"Hello, World!" program]]. This program simply outputs the phrase "Hello, World!" then terminates itself. Let's write "Hello, World!" in Python!

Open up your text editor and create a new file called <code>hello.py</code> containing just this line (you can copy-paste if you want):

<syntaxhighlight lang=python>
print('Hello, World!')
</syntaxhighlight>

The below line is used for Python 3.x.x

<syntaxhighlight lang=python>
print("Hello, World!")
</syntaxhighlight>
You can also put the below line to pause the program at the end until you press anything.

<syntaxhighlight lang=python>
input()
</syntaxhighlight>

This program uses the <code>print</code> function, which simply outputs its parameters to the terminal. By default, <code>print</code> appends a <code>newline</code> character to its output, which simply moves the cursor to the next line.

{{NOTE|In Python 2.x, print is a statement rather than a function.  As such, it can be used without parentheses, in which case it prints everything until the end of the line and accepts a standalone comma after the final item on the line to indicate a multi-line statement. In Python 3.x, print is a proper function expecting its arguments inside parentheses. Using print with parentheses (as above) is compatible with Python 2.x and using this style ensures version-independence.}}


Now that you've written your first program, let's run it in Python! This process differs slightly depending on your operating system.

=== Windows ===

*Create a folder on your computer to use for your Python programs, such as <code>C:\pythonpractice</code>, and save your <code>hello.py</code> program in that folder.
*In the Start menu, select "Run...", and type in <code>cmd</code>. This will cause the Windows terminal to open.
*Type <code>cd \pythonpractice</code> to '''c'''hange '''d'''irectory to your <code>pythonpractice</code> folder, and hit Enter.
*Type <code>hello.py</code> to run your program!

If it didn't work, make sure your PATH contains the python directory. See [[Python Programming/Getting Python|Getting Python]].

=== Mac ===
*Create a folder on your computer to use for your Python programs. A good suggestion would be to name it <code>pythonpractice</code> and place it in your Home folder (the one that contains folders for Documents, Movies, Music, Pictures, etc). Save your <code>hello.py</code> program into it. Open the Applications folder, go into the Utilities folder, and open the Terminal program.
*Type <code>cd pythonpractice</code> to '''c'''hange '''d'''irectory to your <code>pythonpractice</code> folder, and hit Enter.
*Type <code>python ./hello.py</code> to run your program!

{{NOTE|If you have both Python 2 and Python 3 installed (Your machine comes with a version of Python 2 but you can install [https://www.python.org/downloads/ Python 3] as well), you should run <code>python3 hello.py</code>}}

=== Linux ===
*Create a folder on your computer to use for your Python programs, such as <code>~/pythonpractice</code>, and save your <code>hello.py</code> program in that folder.
*Open up the terminal program. In KDE, open the main menu and select "Run Command..." to open {{w|Konsole}}. In GNOME, open the main menu, open the Applications folder, open the Accessories folder,  and select Terminal.
*Type <code>cd ~/pythonpractice</code> to '''c'''hange '''d'''irectory to your <code>pythonpractice</code> folder, and hit Enter.
*Don't forget to make the script executable by chmod +x.
*Type <code>python ./hello.py</code> to run your program!

{{NOTE|If you have both Python version 2.6.1 and Python 3.0 installed (Very possible if you are using Ubuntu, and ran '''sudo apt-get install python3''' to have python3 installed), you should run <code>python3 hello.py</code>}}

=== Linux (advanced) ===

*Create a folder on your computer to use for your Python programs, such as <code>~/pythonpractice</code>.

* Open up your favorite text editor and create a new file called <code>hello.py</code> containing just the following 2 lines (you can copy-paste if you want):<ref>
[[A Quick Introduction to Unix/My First Shell Script]] explains what a hash bang line does.
</ref>

<syntaxhighlight lang=python>
#! /usr/bin/python
print('Hello, world!')
</syntaxhighlight>

{{NOTE|If you have both python version 2.6.1 and version 3.0 installed (Very possible if you are using a debian or debian-based (Ubuntu, Mint, …) distro, and ran '''sudo apt-get install python3''' to have python3 installed),
use
<syntaxhighlight lang=python>
#! /usr/bin/python3
print('Hello, world!')
</syntaxhighlight>
}}

* save your <code>hello.py</code> program in the <code>~/pythonpractice</code> folder.
*Open up the terminal program. In KDE, open the main menu and select "Run Command..." to open Konsole. In GNOME, open the main menu, open the Applications folder, open the Accessories folder,  and select Terminal.
*Type <code>cd ~/pythonpractice</code> to '''c'''hange '''d'''irectory to your <code>pythonpractice</code> folder, and hit Enter.
*Type <code>chmod a+x hello.py</code> to tell Linux that it is an executable program.
*Type <code>./hello.py</code> to run your program!
*In addition, you can also use <code>ln -s hello.py /usr/bin/hello</code> to make a '''s'''ymbolic '''l'''i'''n'''k <code>hello.py</code> to <code>/usr/bin</code> under the name <code>hello</code>, then run it by simply executing <code>hello</code>. 

Note that this mainly should be done for complete, compiled programs, if you have a script that you made and use frequently, then it might be a good idea to put it somewhere in your home directory and put a link to it in /usr/bin. If you want a playground, a good idea is to invoke <code>mkdir ~/.local/bin</code> and then put scripts in there. To make ~/.local/bin content executable the same way /usr/bin does type <code>$PATH = $PATH:~/local/bin</code> (you can add this line to your shell rc file, for example ~/.bashrc).
{{NOTE|File extensions aren't necessary in UNIX-like file-systems. To linux, hello.py means the exact same thing as hello.txt, hello.mp3, or just hello. Linux mostly uses the contents of the file to determine what type it is.
<syntaxhighlight lang="bash">
johndoe@linuxbox ~ $ file /usr/bin/hello
/usr/bin/hello: Python script, ASCII text executable
</syntaxhighlight>
}}

=== Result ===

The program should print:
 Hello, world!
Congratulations! You're well on your way to becoming a Python programmer.

== Exercises ==

#Modify the <code>hello.py</code> program to say hello to someone from your family or your friends (or to [[w:Ada Lovelace|Ada Lovelace]]).
#Change the program so that after the greeting, it asks, "How did you get here?".
#Re-write the original program to use two <code>print</code> statements: one for "Hello" and one for "world". The program should still only print out on one line.

[[Python Programming/Creating Python programs/Solutions|Solutions]]

== Notes ==
<references />

__NOTOC__

{{Python Programming/Navigation|Self Help|Variables and Strings}}

Templates used on this page:

Template:BOOKCATEGORY (view source) (protected)
Template:BookCat (view source) (protected)
Template:BookCat/core (view source) (protected)
Template:BookCat/default (view source) (protected)
Template:Evalx (view source) (protected)
Template:NAIVEBOOKNAME (view source) (protected)
Template:NOTE (edit)
Template:Python Programming (edit)
Template:Python Programming/Navigation (edit)
Template:W (edit)
Template:Wp (edit)
Module:TScope (view source) (protected)
Module:Wikilisp (view source) (protected)

Return to Python Programming/Creating Python Programs.

Retrieved from "https://en.wikibooks.org/wiki/Python_Programming/Creating_Python_Programs"