Python :
Python is a programming language.
Python can be used on a server to create web applications.
What is Python?
Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.
It is used for:
web development (server-side),
software development,
mathematics,
system scripting.
Python was designed for readability, and has some similarities to the English language with influence from mathematics.
Python uses new lines to complete a command, as opposed to other programming languages which often use semicolons or parentheses.
Python relies on indentation, using whitespace, to define scope; such as the scope of loops, functions and classes. Other programming languages often use curly-brackets for this purpose.
To check if you have python installed on a Windows PC, search in the start bar for Python or run the following on the Command Line (cmd.exe):
C:\Users\Your Name>python --version
To check if you have python installed on a Linux or Mac, then on linux open the command line or on Mac open the Terminal and type:
python --version
If you find that you do not have python installed on your computer, then you can download it for free from the following website: https://www.python.org/
Python is an interpreted programming language, this means that as a developer you write Python (.py) files in a text editor and then put those files
into the python interpreter to be executed.
The way to run a python file is like this on the command line:
C:\Users\Your Name>python welcome.py
Where "welcome.py" is the name of your python file.
Let's write our first Python file, called helloworld.py, which can be done in any text editor.
welcome.py
print("Welcome!")
Simple as that. Save your file. Open your command line, navigate to the directory where you saved your file, and run:
C:\Users\Your Name>python welcome.py
The output should read:
Welcome!
The Python Command Line
To test a short amount of code in python sometimes it is quickest and easiest not to write the code in a file. This is made possible because Python can be run as a command line itself.
Type the following on the Windows, Mac or Linux command line:
C:\Users\Your Name>python
Or, if the "python" command did not work, you can try "py":
C:\Users\Your Name>py
From there you can write any python, including our hello world example from earlier in the tutorial:
C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")
Which will write "Hello, World!" in the command line:
C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")
Hello, World!
Whenever you are done in the python command line, you can simply type the following to quit the python command line interface:
exit()
Python Comments:
Comments can be used to explain Python code.
Comments can be used to make the code more readable.
Comments can be used to prevent execution when testing code.
Comments can be placed at the end of a line.
Comments does not have to be text to explain the code.
example:
#This is a comment
print("Hello, World!")
Comments starts with a #, and Python will ignore them:
Python is a programming language.
Python can be used on a server to create web applications.
What is Python?
Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.
It is used for:
web development (server-side),
software development,
mathematics,
system scripting.
Python was designed for readability, and has some similarities to the English language with influence from mathematics.
Python uses new lines to complete a command, as opposed to other programming languages which often use semicolons or parentheses.
Python relies on indentation, using whitespace, to define scope; such as the scope of loops, functions and classes. Other programming languages often use curly-brackets for this purpose.
To check if you have python installed on a Windows PC, search in the start bar for Python or run the following on the Command Line (cmd.exe):
C:\Users\Your Name>python --version
To check if you have python installed on a Linux or Mac, then on linux open the command line or on Mac open the Terminal and type:
python --version
If you find that you do not have python installed on your computer, then you can download it for free from the following website: https://www.python.org/
Python is an interpreted programming language, this means that as a developer you write Python (.py) files in a text editor and then put those files
into the python interpreter to be executed.
The way to run a python file is like this on the command line:
C:\Users\Your Name>python welcome.py
Where "welcome.py" is the name of your python file.
Let's write our first Python file, called helloworld.py, which can be done in any text editor.
welcome.py
print("Welcome!")
Simple as that. Save your file. Open your command line, navigate to the directory where you saved your file, and run:
C:\Users\Your Name>python welcome.py
The output should read:
Welcome!
The Python Command Line
To test a short amount of code in python sometimes it is quickest and easiest not to write the code in a file. This is made possible because Python can be run as a command line itself.
Type the following on the Windows, Mac or Linux command line:
C:\Users\Your Name>python
Or, if the "python" command did not work, you can try "py":
C:\Users\Your Name>py
From there you can write any python, including our hello world example from earlier in the tutorial:
C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")
Which will write "Hello, World!" in the command line:
C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")
Hello, World!
Whenever you are done in the python command line, you can simply type the following to quit the python command line interface:
exit()
Python Comments:
Comments can be used to explain Python code.
Comments can be used to make the code more readable.
Comments can be used to prevent execution when testing code.
Comments can be placed at the end of a line.
Comments does not have to be text to explain the code.
example:
#This is a comment
print("Hello, World!")
Comments starts with a #, and Python will ignore them:
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