If you are a beginner and thinking about starting Python Programming, then the first thing you must know about is How to run python Script.
Once you learn it properly, it will be easy for you to program any code or to find errors in your code if it is not working.
Python is a well-known high-level programming language. It is one of the leading programming languages with relatively simple and easy syntax compared to other programming languages, making it easy to use and more understandable.
Python is not only for data science and scripting. It is basically a fully-featured programming language.
Scripts vs Modules:
Before Starting, You should know about the difference between a Script and a Module. In Computing Language, the word script is used to indicate to a file that contains the logical sequence.
A plain text file that is executed directly by the user is called a Script, on the other hand, a plain text file that is made to be imported and use from outside (that is from another python file) is called Module.
So the main difference is that scripts are designed to be directly executed while modules are meant to be imported.
So You should know about how to run your code written into your modules or scripts .
Is Python a programming language or scripting language?
Firstly you should know the difference between Programming language and Scripting language.
The basic difference between them is their execution process. The programming languages use a compiler while scripting language uses an interpreter.
Also, the programming languages run independently of a parent program while scripting languages run inside another program. C, C++, C#, Java, Pascal, etc. uses Programming languages whereas JavaScript, Shell, Python, Ruby, PHP, Lua, etc. uses Scripting Languages.
The compiler compiles the code and analyzes it at one time and shows all the errors in the code at one time while the interpreter compiles a code line by line and it does not show all the errors in one time.
It checks line by line and stops where it finds any error. This is the reason Why Compiler is faster than Interpreter.
Python is a scripting language. It uses an interpreter instead of the compiler to compile the code. Code is compiled line by line and stops where it finds any error which makes python easy to understand. A beginner can easily identify his/her mistakes as it is easy to find the line of error.
What is the Python Interpreter?
It is not possible for computers to understand the code in the way we humans write. So to make it understandable, an interpreter is used.
The Interpreter acts as the bridge between the program and the system hardware to run the code. It only is responsible for running python scripts.
Basically, the job of an interpreter is to convert the code into a format that is understandable by computers so that they can process the command given by us.
The Python Interpreter works on the REPL environment. REPL stands for Read-Eval-Print-Loop. It means it first Reads the command then evaluates it and then prints the result.
This process keeps on repeating in the loop. For terminating the interpreter, exit() or quit() command is used otherwise it keeps on executing.
A Python Interpreter can run the code in two different ways:
- In the form of a script or module.
- In the form of a piece of code written into an interactive session.
Different versions of Python Interpreter
There are a lot of versions of Python Interpreter like Python2, Python3, Python2.7, Python3.5, Python3.7, and many more. Basically, Interpreters like Python2.7, Python 3.5, etc. are the subversion of Python2 or Python3.
All these versions are slightly different from each other. So you must choose the version which is compatible with your Python code.
How the Interpreter processes the codes?
- It processes the python script in a sequence.
- It compiles the code into a byte code format(Byte code format is a lower-level language that is understandable to computers.)
- At Last, a PVM Machine (Python Virtual Machine) converts the byte code instructions into machine code (in the form of 0s and 1s) so that the computer can understand it and execute those machine code instructions, and gives the final output.
- PVM plays the main role in interpreting the code, So sometimes it alone often called an Interpreter.
How to Start the Python Interpreter?
The simplest way to start the interpreter is open the terminal and use it from the command-Line.
To open the command-Line interpreter in different OS:
- In Windows, the command-Line is called the command prompt or MS-DOS console. To access it go to Start Menu →Run and then type cmd.
- In MAC OS X, the system terminal is accessed through Applications→ Utilities → Terminal.
- In GNU/Linux, the command-Line is accessed by several applications like xterm, Gnome Terminal or Konsole.
Different ways to run Python Script:
- Interactive Mode: It is widely used to run Python Code. To use the interactive mode, open the command prompt on your windows and type “python” and press ENTER. You can run the script line by line in this mode in a sequence. The standard prompt for this mode is >>>, so as soon as you see it, you can write your code according to your requirement. It has a drawback that whenever you close the session, you will lose your code. Every expression and statement is evaluated immediately written by you while working interactively.
- It allows you to test every single piece of code you write which is the best part of this mode. A user can easily identify the errors done by him/her in the code written.
- quit() or exit() are used to exit the interactive mode.
- Command Line: A python file is made by using the extension “.py”. Now, write “python” before the file name in the command prompt to run the script stored in that file by just writing your script and press “Enter”.This is the most basic way to run the Python Scripts. For it, Editors like Sublime or Notepad++ can be used as these are easy to use as compared to other text editors.
- IDE(Pycharm): IDE stands for Integrated Development Environment. We can use Pycharm for it. In Pycharm do the following steps:
- Create a New Project.
- Give any name to the project.
- Then Select the root directory with the project name. Right-click on it→New→ Select the “Python File” Option. Then give any name to that file. Suppose you have given the name “ABC”. So the file will be saved as “ABC.py” file in the project root directory.
- Text Editor (VS Code): You can also use text Editor like VS Code (Visual Studio Code) to run the python scripts. For it you have to do the following:
- Go to the extension section (or press “Ctrl+Shift+X”) on Windows, search the extension “Python” and “Code Runner”. Restart the VS Code after it.
- Create a new file with any desired name, suppose “ABC.py” and write the code you want to perform.
- Then, Right-click anywhere in the text area →Select the option”Run Code” or press “Ctrl+Alt+N” to run the code.
Batch Files:
A batch file is created to specify the commands. It is used so that a user need not remember every time which version is to use to run the python program.
Hashbang or Shebang:
It is character combination of #!. This is a special character sequence in a script that specifies which program is called to run the script. It is always on the top of the file and denoted by the character #! followed by the path to the Interpreter program.
Comments in Python Scripts:
Python is known for its easy-to-use feature. Sometimes we wish to give some explanation or to put any comment about any particular code just near to it without its actual involvement while running the program so that it will be easy to understand that code to use in the future. It also helps other users, team members, or colleagues to understand the logic behind that particular code especially in teamwork where the different work has been divided into different members. This makes it easy to work. You can add the comments in python by simply adding a hash (#) before using any statement.
Conclusion:
The Python Interpreter is very useful in Python to run any code or we have to find the errors in the code.
By reading this article, you may now know about different ways and modes in which the Python commands or scripts can be run, how an interpreter works.
So after knowing all that, choose the best option according to your task requirement so that you can be faster, flexible, and more productive with your work.
