Python is a widely used programming language that offers a plethora of features and functionalities for developers. One of the most powerful features of Python is its ability to execute shell commands within a script. This allows developers to interact with the operating system and perform various tasks such as creating files, copying data, and launching applications. In this article, we will explore the process of launching and waiting for shell command termination in a Python script.
To begin with, let's understand what a shell command is. A shell command is a series of instructions or tasks that are executed in a sequential manner by the operating system's command-line interface. These commands can be used to perform a wide range of tasks, from simple file operations to more complex system configurations.
In order to execute shell commands in a Python script, we need to use the 'subprocess' module. This module provides a simple interface for creating and managing child processes. It also allows us to execute shell commands and retrieve their output.
The first step is to import the 'subprocess' module in our Python script. We can do this by using the 'import' keyword followed by the module name.
```
import subprocess
```
Next, we need to define the shell command that we want to execute. For this example, let's say we want to create a new file named 'test.txt' in our current working directory. We can use the 'touch' command to achieve this.
```
command = 'touch test.txt'
```
Now, we can use the 'subprocess.call()' function to execute our shell command. This function takes in the command as an argument and executes it in a new child process.
```
subprocess.call(command, shell=True)
```
The 'shell' parameter is set to 'True' to indicate that the command should be executed in a shell. This is necessary for commands that require a shell environment, such as 'touch'.
Once the command is executed, we can check if it was successful by using the 'print()' function to display the output of the command.
```
print("File created successfully!")
```
However, in some cases, we may need to wait for the command to finish its execution before proceeding with the rest of the script. For this, we can use the 'subprocess.check_call()' function. This function works similar to 'subprocess.call()', but it waits for the command to complete its execution before moving on to the next line of code.
```
subprocess.check_call(command, shell=True)
```
We can also retrieve the output of the command by storing it in a variable and then using the 'subprocess.check_output()' function.
```
output = subprocess.check_output(command, shell=True)
```
Once the command has completed its execution, we can use the 'print()' function to display the output to the user.
```
print(output)
```
It is important to note that if the command encounters an error during its execution, it will raise a 'CalledProcessError' exception. This can be handled using the 'try-except' block to ensure that the script does not terminate abruptly.
In conclusion, Python's 'subprocess' module provides a convenient way to execute shell commands within a script. By using the 'subprocess.call()' and 'subprocess.check_call()' functions, we can launch and wait for shell command termination, while the 'subprocess.check_output()' function allows us to retrieve the output of the command. With
