Python Tutorial

Introduction Python Features Python Applications System requirements for Python Python Installation Python Examples Python Basics Python Indentation Python Variables Python Data Types Python IDE Python Keywords Python Operators Python Comments Python Pass Statement

Python Conditional Statements

Python if Statement Python elif Statement Python If-else statement Python Switch Case

Python Loops

Python for loop Python while loop Python Break Statement Python Continue Statement Python Goto Statement

Python Arrays

Python Array Python Matrix

Python Strings

Python Strings Python Regex

Python Built-in Data Structure

Python Lists Python Tuples Python Lists vs Tuples Python Dictionary Python Sets

Python Functions

Python Function Python min() function Python max() function Python User-define Functions Python Built-in Functions Python Recursion Anonymous/Lambda Function in Python python apply() Function Python lambda() Function

Python File Handling

Python File Handling Python Read CSV Python Write CSV Python Read Excel Python Write Excel Python Read Text File Python Write Text File Read JSON File in Python

Python Exception Handling

Python Exception Handling Python Errors and exceptions Python Assert

Python OOPs Concept

OOPs Concepts in Python Classes & Objects in Python Inheritance in Python Polymorphism in Python Python Encapsulation Python Constructor Python Super function Python Static Method Static Variables in Python Abstraction in Python

Python Iterators

Iterators in Python Yield Statement In Python

Python Generators

Python Generator

Python Decorators

Python Decorator

Python Functions and Methods

Python Built-in Functions Python String Methods Python List Methods Python Dictionary Methods Python Tuple Methods Python Set Methods

Python Modules

Python Modules Python Datetime Module Python Math Module Python Import Module Python Time Module Python Random Module Python Calendar Module CSV Module in Python Python Subprocess Module Python Subprocess

Python MySQL

Python MySQL Python MySQL Client Update Operation Delete Operation Database Connection Creating new Database using Python MySQL Creating Tables Performing Transactions

Python MongoDB

Python MongoDB

Python SQLite

Python SQLite

Python Data Structure Implementation

Python Stack Python Queue Python Linked List Python Hash Table Python Graph

Python Advance Topics

Speech Recognition in Python Face Recognition in Python Python Linear regression Python Rest API Python Command Line Arguments Python JSON Python Virtual Environment Type Casting in Python Python Collections Python Commands Python Data Visualization Python Debugger Python DefaultDict Python Enumerate

Python 3

Anaconda in Python 3 Anaconda python 3 installation for windows 10 List Comprehension in Python3

Misc

Python PPTX Python Pickle Python Seaborn Python Coroutine Python EOL Python Infinity Python math.cos and math.acos function Python Project Ideas Based On Django Reverse a String in Python Reverse a Number in Python Python Word Tokenizer Python Trigonometric Functions Python try catch exception GUI Calculator in Python Implementing geometric shapes into the game in python Installing Packages in Python Python Try Except Python Sending Email Socket Programming in Python Python CGI Programming Python Data Structures Python abstract class Python Compiler Python K-Means Clustering NSE Tools In Python Operator Module In Python Palindrome In Python Permutations in Python Pillow Python introduction and setup Python Functionalities of Pillow Module Python Argmin Python whois Python JSON Schema Python lock Return Statement In Python Reverse a sentence In Python tell() function in Python Why learn Python? Write Dictionary to CSV in Python Write a String in Python Binary Search Visualization using Pygame in Python Latest Project Ideas using Python 2022 Closest Pair of Points in Python ComboBox in Python Python vs R Best resources to learn Numpy and Pandas in python Check Letter in a String Python Python Console Python Control Statements Convert Float to Int in Python using Pandas Difference between python list and tuple Importing Numpy in Pycharm Python Key Error Python NewLine Python tokens and character set Python Strong Number any() Keyword in python Best Database in Python Check whether dir is empty or not in python Comments in the Python Programming Language Convert int to Float in Python using Pandas Decision Tree Classification in Python End Parameter in python __GETITEM__ and __SETITEM__ in Python Python Namespace Python GUI Programming List Assignment Index out of Range in Python List Iteration in Python List Index out of Range Python for Loop List Subtract in Python Python Empty Tuple Python Escape Characters Sentence to python vector Slicing of a String in Python Executing Shell Commands in Python Genetic Algorithm in python Get index of element in array in python Looping through Data Frame in Python Syntax of Map function in Python After Python What Should I Learn Python AIOHTTP Alexa Python Artificial intelligence mini projects ideas in python Artificial intelligence mini projects with source code in Python Find whether the given stringnumber is palindrome or not First Unique Character in a String Python Python Network Programming Python Interface Python Multithreading Python Interpreter Data Distribution in python Flutter with tensor flow in python Front end in python Iterate a Dictionary in Python Iterate a Dictionary in Python – Part 2 Allocate a minimum number of pages in python Assertion Errors and Attribute Errors in Python Checking whether a String Contains a Set of Characters in python Python Control Flow Statements *Args and **Kwargs in Python Bar Plot in Python Conditional Expressions in Python Function annotations() in Python How to Write a Configuration file in Python Image to Text in python import() Function in Python Import py file in Python Multiple Linear Regression using Python Nested Tuple in Python Python String Negative Indexing Reading a File Line by Line in Python Python Comment Block Base Case in Recursive function python ER diagram of the Bank Management System in python Image to NumPy Arrays in Python NOT IN operator in Python One Liner If-Else Statements in Python Sklearn in Python Python Ternary Operators Self in Python Python vs Java Python Modulo Python Packages Python Syntax Python Uses Python Bitwise Operators Python Identifiers Python Matrix Multiplication Python AND Operator Python Logical Operators Python Multiprocessing Python Unit Testing __init__ in Python Advantages of Python Is Python Case-sensitive when Dealing with Identifiers Python Boolean Python Call Function Python History Python Image Processing Python main() function Python Permutations and Combinations Difference between Input() and raw_input() functions in Python Conditional Statements in python Confusion Matrix Visualization Python Python Algorithms Python Modules List Difference between Python 2 and Python 3 Is Python Case Sensitive Method Overloading in Python Python Arithmetic Operators Assignment Operators in Python Is Python Object Oriented Programming language Division in Python Python exit commands Continue And Pass Statements In Python Colors In Python Convert String Into Int In Python Convert String To Binary In Python Convert Uppercase To Lowercase In Python Convert XML To JSON In Python Converting Set To List In Python Covariance In Python CSV Module In Python Decision Tree In Python Difference Between Yield And Return In Python Dynamic Typing In Python

How to

How to Substring a String in Python How to Iterate through a Dictionary in Python How to convert integer to float in Python How to reverse a string in Python How to take input in Python How to install Python in Windows How to install Python in Ubuntu How to install PIP in Python How to call a function in Python How to download Python How to comment multiple lines in Python How to create a file in Python How to create a list in Python How to declare array in Python How to clear screen in Python How to convert string to list in Python How to take multiple inputs in Python How to write a program in Python How to compare two strings in Python How to create a dictionary in Python How to create an array in Python How to update Python How to compare two lists in Python How to concatenate two strings in Python How to print pattern in Python How to check data type in python How to slice a list in python How to implement classifiers in Python How To Print Colored Text in Python How to develop a game in python How to print in same line in python How to create a class in python How to find square root in python How to import numy in python How to import pandas in python How to uninstall python How to upgrade PIP in python How to append a string in python How to open a file in python How to Open a file in python with Path How to run a Python file in CMD How to change the names of Columns in Python How to Concat two Dataframes in Python How to Iterate a List in Python How to learn python Online How to Make an App with Python

Sorting

Python Sort List Sort Dictionary in Python Python sort() function Python Bubble Sort

Programs

Factorial Program in Python Prime Number Program in Python Fibonacci Series Program in Python Leap Year Program in Python Palindrome Program in Python Check Palindrome In Python Calculator Program in Python Armstrong Number Program in Python Python Program to add two numbers Anagram Program in Python Even Odd Program in Python GCD Program in Python Python Exit Program Python Program to check Leap Year Operator Overloading in Python Pointers in Python Python Not Equal Operator Raise Exception in Python Salary of Python Developers in India What is a Script in Python

Subprocess Module in Python

What is a Process?

Every program will have its respective system state, i.e., the state in which it is running. A program that is in a running state or in a state of being executed is known as a Process. The word process itself defines that the functioning takes place in sequential order. In other words, the statements in the process are executed in a sequential control flow. This can be defined as the main thread process in some of the relevant and particular situations.

Whenever you work with a PC, you'll constantly be involved and work with the programs. A process is the working framework's reflection of a running project. Thus, working with PC generally include processes. When you think of performing any kind of operation within the PC, many processes will be involved in order to complete that task. A normal working framework will report hundreds or even a huge number of running cycles. Many instructions can be executed simultaneously within the CPU to make things faster and optimized. Thus, you might consider how a large number of cycles can seem to run simultaneously.

So, the working framework is a magnificent multitasker, as it must be. The CPU is the mind of a PC. However, it works within a fraction of a second. Performing multiple tasks keeps the CPU occupied. The working framework monitors processes in a cycle or interaction control block.

What is a Subprocess?

Our PC runs subprocesses constantly. Any activity we do on our PC includes conjuring a subprocess. That stays genuine regardless of whether we are composing a basic script or program in python. As a matter of fact, by simply perusing this article, you're running a great deal of cycles like an organization director or the web program.

The idea of the subprocess may appear to be dark regardless of whether you've been getting the hang of programming for some time. To be more precise, a subprocess is a computerized process that is, in turn, created by another process. This article will investigate the primary idea of the subprocess and how to utilize the Python subprocess standard library.

It is just a chain of actions where the work is divided into fragments. On the whole, if the process is supposed to do some work or a task that consumes 10 minutes of time, the computerized process divides the work into fragments where the fragmented work is distributed among the subprocesses. This type of fragmentation is done in order to perform the given task within less amount of time using the subprocesses, which work simultaneously.

Let us discuss the concept of subprocess with a real-time example. Let us consider a software company in which the tasks that are given by the higher companies should be completed on time. So, the head of the company is not going to do all the work that is supposed to be done. He will hire a few people to work under him in order to complete the given work on time by distributing the work so that those hired people can work simultaneously.

The major advantage of this is that the work is being done in a very less amount of time and the people need not work very hard to complete the work. The company here is Computer. The head of the company is Process. The people that the process hired is Subprocess. So, in order to complete the task within less amount of time, the processes are divided into subprocesses which begin their work simultaneously.

The process is referred to be a Parent, whereas the subprocess is referred to be a child of that particular parent. As we know, one parent can have many children. In the same way, one process can have a huge number of subprocesses. The processes and subprocesses always intend to perform independently so that the destruction of any one of the processes or subprocesses will not lead to the termination of the entire procedure. Sometimes, the subprocesses inherit few characteristics from the processes for completing the desired task or operation. The information is mostly maintained in the form of a table within the process so that the fragmentation of the process into subprocesses becomes easier.  

Why is the Subprocess module used in Python?

  • It is used to run any type of operating system commands and manipulate the output later.
  • It helps us call external commands, including methods, functions, etc.
  • With the help of subprocess modules, you can be able to capture the output of the commands or type convert the output from one command to another.
  • It acts like a communicator between the shell and the output script.

Common steps that must be done to implement the subprocess module in Python:

1. Firstly the subprocess module must be imported by using “ import “.

# import subprocess module
import subprocess

2. After importing the subprocess module, you can give the desired command using the subprocess module by calling the required method with the word or keyword " subprocess ". The methods that we use and the commands we produce completely depend on the Operating system we use. Mostly, the " Popen() " method or function is used. Along with the method " Popen() ", we can also use the " run() " method.

The methods with subprocess and that can be used in implementing subprocess module are:

  • Popen()
  • check_call()
  • check_output()
  • run()  [ This is a general function ]
# using the run() function
subprocess.run(command)


#         or


# using the Popen() function
subprocess.Popen(command)


#         or


# using check_call() function
subprocess.check_call(command)


#         or


# using check_output() function
subprocess.check_output(command)

Simple program syntax which can implement subprocess module:

# to implement the subprocess module in python


# import subprocess module
import subprocess


# using the run() function
subprocess.run(command)

Let us discuss an example problem using all functions:

1. run() :

# to implement the subprocess module in python using run()
# import subprocess module
import subprocess
# using the run() function
subprocess.run('dir')

2. Popen() :

# to implement the subprocess module in python using Popen()
# import subprocess module
import subprocess
# using the Popen() function
subprocess.Popen('dir')

3. check_call() :

# to implement the subprocess module in python using check_call()
# import subprocess module
import subprocess
# using the check_call() function
subprocess.check_call(['False'])

4. check_output() :

# to implement the subprocess module in python using check_output()
# import subprocess module
import subprocess
# using the check_output() function
subprocess.check_output('dir')

All the programs that are listed above will produce errors when they are executed. The reason for producing errors is that the given commands are not accepted in the form of strings. They are considered to be normal statements but not string commands.

To overcome these errors, we generally introduce a command, normally called an argument “ shell “, and we set it to True to express the given command in the form of a string. You can also produce the output without using the " shell " argument. For doing so, you need to put the commands inside the list, i.e., represent the commands in the form of a list so that the compiler identifies it as a string.  

Let us examine the same program again by using self and setting it to True “:

Program using run() function:

# to implement the subprocess module in python using run()
# import subprocess module
import subprocess
# using the run() function
subprocess.run('dir',shell=True)

Output:

Volume in drive D is Data
Volume Serial Number is 40D9-C745 
Directory of D:\downloads hdd\2-2


09-07-2022  21:38    <DIR>          .
08-07-2022  21:48    <DIR>          ..
30-06-2022  20:03             1,515 #class HumanSpecies is being declared fo.py
21-06-2022  14:01           528,681 B.Tech_2-2 Sem R20_Regular_July 2022.pdf
23-04-2022  20:51         3,612,851 daa unit 1.pdf
23-04-2022  20:51         1,774,354 daa unit 2.pdf
23-04-2022  20:52         4,855,826 daa unit 3.pdf
23-04-2022  20:56         1,971,782 dbms.pdf
30-06-2022  21:23               575 import csv.py
23-04-2022  20:45           128,387 p&s ASSIGNMENT-I.pdf
29-06-2022  22:09             1,513 test.py
27-06-2022  22:49                38 Untitled-1.py
09-07-2022  21:38               157 Untitled-11.py
27-06-2022  23:00                32 Untitled-2.py
27-06-2022  23:10                32 Untitled-3.py
30-06-2022  20:03             2,018 Untitled-4.py
30-06-2022  20:58               843 Untitled-6.py
30-06-2022  22:02               259 Untitled-7.py
              16 File(s)     12,878,863 bytes
               2 Dir(s)  989,647,040,512 bytes free

These are the files present in my directory. All the details, including time, date, and space occupancy, will also be printed along with the name of the files.

Program using Popen() function:

# to implement the subprocess module in python using Popen()
# import subprocess module
import subprocess
# using the Popen() function
subprocess.Popen('dir',shell=True)

Output

Volume in drive D is Data
Volume Serial Number is 40D9-C745


Directory of D:\downloads hdd\2-2


09-07-2022  21:38    <DIR>          .
08-07-2022  21:48    <DIR>          ..
30-06-2022  20:03             1,515 #class HumanSpecies is being declared fo.py
21-06-2022  14:01           528,681 B.Tech_2-2 Sem R20_Regular_July 2022.pdf
23-04-2022  20:51         3,612,851 daa unit 1.pdf
23-04-2022  20:51         1,774,354 daa unit 2.pdf
23-04-2022  20:52         4,855,826 daa unit 3.pdf
23-04-2022  20:56         1,971,782 dbms.pdf
30-06-2022  21:23               575 import csv.py
23-04-2022  20:45           128,387 p&s ASSIGNMENT-I.pdf
29-06-2022  22:09             1,513 test.py
27-06-2022  22:49                38 Untitled-1.py
09-07-2022  21:38               157 Untitled-11.py
27-06-2022  23:00                32 Untitled-2.py
27-06-2022  23:10                32 Untitled-3.py
30-06-2022  20:03             2,018 Untitled-4.py
30-06-2022  20:58               843 Untitled-6.py
30-06-2022  22:02               259 Untitled-7.py
       16 File(s)     12,878,863 bytes
       2 Dir(s)  989,647,040,512 bytes free

The above program prints all the folders that are present in the current directory using the command “ dir “. We can observe that the output of the first program is equal to the output of the second program. So, any one of these methods can be used in order to implement a subprocess in Python.



ADVERTISEMENT
ADVERTISEMENT