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Mike Driscoll

7 Oct, 9 tweets, 5 min read

Concurrency is a hard topic. So today we're going to talk about multiprocessing in #Python

Join for me another fun mini-thread!

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The Pros of using `multiprocessing` in #Python (part 1 of 2)

🐍 Processes use separate memory space
🐍 Code can be more straightforward compared to threads
🐍 Uses multiple CPUs / cores
🐍 Avoids the Global Interpreter Lock (GIL)

The Pros of using `multiprocessing` in #Python (part 2 of 2)

🐍 Child processes can be killed (unlike threads)
🐍 The multiprocessing module has an interface similar to `threading.Thread`
🐍 Good for CPU-bound processing (encryption, binary search, matrix multiplication)

The Cons of using `multiprocessing in #Python

🐍 Interprocess communication is more complicated
🐍 Memory footprint is larger than threads

Here is a small example of using `multiprocessing` in #Python

In this example, you use a `for` loop to create multiple `Process` instances that target the `doubler()` function.

Then you `start()` the processes. The output is in the second screenshot

You can name your processes in #Python. This makes debugging easier since each process has a specific name

You can add locks to your processes in #Python so that the processes don't try to access the same thing at the same time:

@mousevspython

If you'd like to learn more about `multiprocessing` in #Python, check out my tutorial @mousevspython

blog.pythonlibrary.org/2016/08/02/pyt…

I hope you enjoyed learning about the basics of `multiprocessing` in #Python with me. Be sure to share this thread with your friends and follow me for more Python tips!

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More from @driscollis

Mike Driscoll

@driscollis

7 Oct

I use a lot of #Python resource. Here are some of my favorite!

Yes, it's another thread!

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Mouse vs Python, which is my own blog, is a resource I use myself because I write it for my future self as well as for you.

I put what I am currently working on or neat code snippets on there that I think I will use

blog.pythonlibrary.org

@doughellmann

If I need to know about a specific module in #Python, I still check the Python Module of the Week website by @doughellmann

pymotw.com/3/

Read 11 tweets

Mike Driscoll

@driscollis

7 Oct

Do you know how to make a #Python class method act like an attribute?

You can do that by turning the method into a `property`

Learn how in this thread!

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The first step is to look at a regular #Python class.

The following `Person` class has a method called `full_name()`. To get the full name of the `Person`, you must call `full_name()`

Wouldn't it be nice if you could just use dot notation instead of calling it?

@property

In #Python, you can turn the method into a `property` using the `@property` decorator

Once you do that, you can then use dot notation to access the `full_name()` method as if it were an instance attribute!

Read 10 tweets

Mike Driscoll

@driscollis

6 Oct

There are a lot of "magic methods" or "dunder methods" in #Python.

I'll be talking about these for a few days, so stay tuned!

First off is `__init__()` and `__repr__()`

A magic method is a #Python class method that begins and ends with double-underscores

Most classes require you to create an `__init__()`

`__init__()` is short for initialization and initializes the instance

Sometimes, `__init__()` is called a constructor. However, I have seen it claimed that you need to combine `__new__()` with `__init__()` for it to be a true constructor

`__new__()` is used for allocating memory while `__init__()` is used for initializing the instance

Read 7 tweets

Mike Driscoll

@driscollis

6 Oct

When using a class in #Python, you may notice that the first argument in all the class's methods is "self"

What is up with that? Well, let's talk about it!

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First of all, "self" is a convention that refers to the instance that is created when you instantiate a class. You don't have to name it "self", but that is best practice

Here is an example where "self" is replaced with "this"

You use "self" to be able to access instance attributes across methods in a #Python class.

Here is an example where you initialize (__init__) `self.name` and then use `self.name` later on when you call the `walk()` method:

Read 5 tweets

Mike Driscoll

@driscollis

6 Oct

Whenever you talk about classes in #Python, you will probably see the `super()` function mentioned.

The most common way of writing `super()` in a #Python class is to write it like this:

You can also call `super()` with the class name and self passed in, but most #Python developers see that as redundant since it is the equivalent of `super().__init__()`

Read 5 tweets

Mike Driscoll

@driscollis

6 Oct

Today I'm going to start a series on #Python classes.

According to the Python docs: "Creating a new class creates a new type of object, allowing new instances of that type to be made. Each class instance can have attributes attached to it for maintaining its state. "

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Here is an example of a #Python class that has a single attribute: `name`

🐍 `animal_1` is an instance of the `Animal()` class
🐍 `animal_2` is another instance of the `Animal()` class

You can access an instance's attributes using the "." operator

A #Python class always inherits from the `object` base class. In Python 3, you do not need to specify that you inheriting from `object`

That means that the following two examples are doing the same thing:

Read 4 tweets

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