Popen vs. Run

Attribute	Popen	Run
Functionality	Allows for more control over the input/output streams of a process	Simple way to run a command and get its output
Usage	More suitable for complex interactions with a process	Quick and easy way to run a command
Return Value	Returns a Popen object	Returns the output of the command
Blocking	Can be used in a non-blocking way	Blocks until the command is finished

Introduction

When working with subprocesses in Python, developers often have to choose between using the Popen or Run functions from the subprocess module. Both functions are used to run external commands, but they have some key differences in terms of how they handle the execution of these commands. In this article, we will compare the attributes of Popen and Run to help developers understand when to use each function.

Functionality

The Popen function is a more low-level function that allows for more control over the subprocess. It returns a Popen object that represents the running subprocess, which can be used to interact with the process while it is running. This includes reading from and writing to the process's standard input, output, and error streams. On the other hand, the Run function is a higher-level function that simplifies the process of running a command and waiting for it to complete. It returns a CompletedProcess object that contains information about the completed process, such as the return code and output.

Usage

When using the Popen function, developers have to manually manage the subprocess by calling methods on the Popen object. This includes handling input and output streams, as well as waiting for the process to complete. In contrast, the Run function takes care of these details automatically, making it easier to run a command and get the results. This makes Run a more convenient option for simple use cases where the developer does not need fine-grained control over the subprocess.

Control

One of the main differences between Popen and Run is the level of control they provide over the subprocess. With Popen, developers can interact with the subprocess while it is running, allowing them to send input to the process, read its output, and handle errors as they occur. This level of control is useful for more complex scenarios where the developer needs to manage the subprocess in a specific way. On the other hand, Run abstracts away these details and simply runs the command, waiting for it to complete before returning the results. This lack of control may be limiting in some cases, but it makes Run easier to use for simple tasks.

Performance

When it comes to performance, there is a slight difference between Popen and Run. Since Popen provides more control over the subprocess, it may be slightly faster in some cases where the developer needs to interact with the process while it is running. However, this added control comes at the cost of complexity, as developers have to manage the subprocess manually. On the other hand, Run simplifies the process of running a command and waiting for it to complete, which may result in slightly slower performance due to the overhead of managing the process automatically.

Flexibility

Another factor to consider when choosing between Popen and Run is flexibility. Popen allows developers to customize how the subprocess is run by specifying options such as the working directory, environment variables, and input/output streams. This level of customization is useful for scenarios where the developer needs fine-grained control over the subprocess. On the other hand, Run provides a more streamlined interface that may be easier to use for simple tasks, but lacks the flexibility of Popen in terms of customization options.

Conclusion

In conclusion, both Popen and Run have their own strengths and weaknesses when it comes to running external commands in Python. Popen provides more control and flexibility, making it a good choice for complex scenarios where the developer needs to interact with the subprocess in a specific way. On the other hand, Run simplifies the process of running a command and waiting for it to complete, making it a more convenient option for simple tasks. Ultimately, the choice between Popen and Run depends on the specific requirements of the project and the level of control and flexibility needed by the developer.