HometechnologyWhat is a subprocess in Python?

What is a subprocess in Python?

Many Python programs and scripts run in the background, performing various tasks and activities; these are processes. The Python process can even have its subprocesses, just like a snake species can have its subspecies. Although this knowledge may seem overwhelming, it has the potential to make our tasks much easier to handle.

Do you know that Python allows you to run outside processes? The Subprocess in Python module will be used to demonstrate this functionality. Let’s get started with a quick primer on the subprocess in Python.

What is a subprocess in Python?

A process creates a subprocess to carry out work within the more extensive process. Let’s elaborate; during a program’s execution, it executes a series of tasks known as processes. Almost every process consists of subtasks that must be finished before the whole process can be considered complete.

The use of subprocess in Python becomes relevant at this point. A process can create a child’s process to perform a trivial task while the parent process keeps going. It results in a more streamlined, effective method of handling data and RAM.

Devices would quickly run out of memory if they created a new process for every task that a process needed to complete. As a result of the extra work it would cause for device processors, this approach would also be very inefficient.

You can increase the number of processes you run in parallel by breaking up larger ones into smaller ones that can handle simpler tasks within the larger ones. In Python, this is accomplished with the help of the multiprocessing package, which allows for the use of multiple CPUs. Python, an older language, did not aid in that performance because devices did not have as many processors back then.

Subprocess in Python

You can create new processes, attach them to their input/output/error pipes, and collect their exit codes with the help of Python’s subprocess module.

Following the advice in the official Python documentation, we can use the Subprocess to access the system commands. Using the subprocess module, for instance, we can launch processes, send data and receive results from them, and handle error conditions.

The run() function is recommended as the standard method for invoking child processes. You can use the underlying Popen interface directly for more complex use cases.

Python 3.5 introduced the run() function; for backward compatibility, see the older high-level API section.

Designed to take the place of os.system(), os.spawn*(), os.popen*(), popen2.*(), and commands*, it provides a more high-level interface than the other modules (). Many examples are carbon copies of those used for os and popen, making it easier to draw parallels between the Subprocess and the other modules.

The subprocess in the Python module

You can launch new processes within a Python script using the Subprocess, a built-in module. It is a great help and the recommended method when your Python code needs to run multiple processes simultaneously or call an external program or command.

The subprocess module’s usefulness lies in the fact that the user can directly control the child process’s inputs, outputs, and errors in Python. This feature adds power and flexibility to the practice of calling subprocesses, allowing, for example, for the output of the Subprocess to be used as a variable in the rest of the Python script.

The module debuted in Python 2.4 to provide an alternative to existing functions like the os.system. Furthermore, the run() function is the recommended method of accessing this module as of Python 3.5.

The Subprocess Module

Let’s check out a few examples now!

  • The subprocess.call() function

Python requires the subprocess module to be imported before you can use its associated functions.

The subprocess.call() function executes the given command and returns the success or failure of the operation.

  • The subprocess.run() command

The above example shows that the call() function returns the command’s exit status. Our ability to verify input and output values is severely hindered.

To do this, we can use the Subprocess.run() function, which allows us to run a bash or system script from within Python and provides us with the exit status of the command.

Additionally, the arguments given to the function are returned. This aids in ensuring that only valid data is being fed into the system scripts.

  • The Subprocess.Open() function

Using the subprocess.Open() function, we can have child programs run in a separate process within the parent program.

  • Subprocess call()

To run an application, you can use the call() method available on Subprocess in Python. In this case, the parameter is a list, and the first item in the list must be the name of the executable being used.

A practical guide to your program’s subprocess module

You should feel comfortable with Python subprocesses for your software development projects. Several factors, such as potential new modes of interaction, must be considered before you can make progress with subprocesses. Read on for some parting thoughts on processes within processes to mull over.

  • Using a subprocess in Pythonis an excellent tool for improving the performance of your program.
  • The call() and Popen() functions are the primary means of invoking child processes.
  • When using Popen(), the wait() method is required to get the full runtime result of a process.
  • Deadlocks can occur when using the wait() method in conjunction with the stdout/stderr=PIPE directives.
  • When the wait() method is inappropriate, you can switch to the communicate() method.

These details and the preceding examples equip you to implement the subprocess in Python module.


When running a Python script, you can use the subprocess module and its associated Subprocess.run() function to communicate with and modify the behavior of other processes.

If you’re interested in learning subprocess in Python or getting certified in Python modules, you can also check out Simplilearn online courses. You can track your progress, take quizzes to ensure you’re learning the material, and even get hands-on practice with the included exercises. A printable completion certificate is available for each class.


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