Are you struggling with importing modules in Python without causing unintended side effects? Well, have we got the solution for you! Introducing safe module imports using multiprocessing. In this tutorial, we’ll show you how to safely import a main module and avoid starting new processes or causing other issues when running your code with multiple processes.
First, let’s install the `multiprocessing` library:
# This script installs the multiprocessing library using the pip command.
# First, we need to import the subprocess module to run commands in the terminal.
import subprocess
# Next, we use the subprocess module to run the pip command and install the multiprocessing library.
subprocess.run(["pip", "install", "multiprocessing"])
# The subprocess.run() function takes a list of strings as its argument, where the first element is the command to be executed and the following elements are the arguments for that command.
# The "pip install multiprocessing" command will install the multiprocessing library on the system.
# Note: It is important to use the subprocess module when running commands in the terminal to avoid potential security risks.
# Finally, the library is now installed and ready to be used in our code.
Once installed, import the library in your Python script:
# Import the multiprocessing library and the freeze_support function
from multiprocessing import Process, freeze_support
# The freeze_support function is used to support Windows systems
# It is necessary to call this function before creating any processes
# Define a function to be executed by the process
def print_message(message):
print(message)
# Create a process that will execute the print_message function with the message "Hello World"
process = Process(target=print_message, args=("Hello World",))
# Start the process
process.start()
# Wait for the process to finish before continuing with the main script
process.join()
# Print a message to indicate that the process has finished
print("Process finished executing")
Now that we have our tools ready to go, let’s create a new module called `my_module.py`. This will be our main module that we want to safely import into other scripts without causing any issues:
# my_module.py
# This is a new module that can be safely imported into other scripts without causing any issues.
# Defining a function called "hello" that takes in no parameters.
def hello():
# Printing a string to the console.
print("Hello from my_module!")
# The function is not called, so it will not be executed.
# To execute the function, we need to call it in our main script.
Next, let’s create a new script called `main.py`. This will be the main entry point for our code and it will safely import `my_module.py`:
# main.py
# Importing necessary modules
from multiprocessing import Process, freeze_support
import my_module
# Defining a function to run the code from my_module
def run():
my_module.hello() # Calling the hello() function from my_module
# Checking if the script is being run directly
if __name__ == '__main__':
freeze_support() # Required for Windows to prevent DLL load failure: https://stackoverflow.com/a/41905276
p = Process(target=run) # Creating a new process with the target set to the run() function
p.start() # Starting the process
p.join() # Waiting for the process to finish before continuing with the main script
# The purpose of this script is to serve as the main entry point for our code. It imports the necessary modules and defines a function to run the code from my_module. It also checks if the script is being run directly and creates a new process to run the code in parallel. The freeze_support() function is necessary for Windows to prevent a DLL load failure.
In this example, we’re using the `freeze_support` function to prevent DLL load failures on Windows when running our code with multiple processes. This is not necessary for other operating systems like Linux or macOS.
Now that we have our main script ready, let’s test it out! Run `main.py` and you should see the output: “Hello from my_module!”
That’s it! You can now safely import your main module into other scripts without causing any issues or unintended side effects.