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I'm new to the subprocess module and the documentation leaves me wondering what the difference is between subprocess.popen and subprocess.run. Is there a difference in what the command does? Is one just newer? Which is better to use?
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The subprocess module defines one class, Popen and a few wrapper functions that use that class. The constructor for Popen takes arguments to set up the new process so the parent can communicate with it via pipes. It provides all of the functionality of the other modules and functions it replaces, and more.
Python method popen() opens a pipe to or from command. The return value is an open file object connected to the pipe, which can be read or written depending on whether mode is 'r' (default) or 'w'.
The subprocess. check_output() is used to get the output of the calling program in python. It has 5 arguments; args, stdin, stderr, shell, universal_newlines. The args argument holds the commands that are to be passed as a string.
Popen with context managers is documented and was added in Python 3.2.
subprocess.run was added in Python 3.5 as a simplification over subprocess.Popen when you just want to execute a command and wait until it finishes, but you don't want to do anything else meanwhile. For other cases, you still need to use subprocess.Popen.
The main difference is that subprocess.run executes a command and waits for it to finish, while with subprocess.Popen you can continue doing your stuff while the process finishes and then just repeatedly call subprocess.communicate yourself to pass and receive data to your process.
Note that, what subprocess.run is actually doing is invoking for you the Popen and communicate, so you don't need to make a loop to pass/receive data nor wait for the process to finish.
Check the official documentation for information of which parameters of subprocess.run are passed to Popen and which to communicate.
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