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Python 3.8 Feature Selection – What’s New?

Python 3.8 – awesome features!

This article will put some light on three the most useful, in our opinion, features that come in the latest Python release. The purpose of such selection is to quickly introduce you with new and cool stuff that came with a 3.8 version and allow you to use it just right now.

1. Consistent logic with a brand new operator – walrus

walrus
source: https://unsplash.com/

Why walrus? Probably, because of a visual representation that may be interpreted as two eyes and long parallel teeth – :=.

It’s a very useful operator that allows writing more consistent code and it’s something that I personally missed in any of programming languages. Let’s dive into some examples:

Let’s have some data to process:

data = {    
  'users': [ 'peter', 'john' ]
}    

We’d like to check if there are some users in our data and then print them amount. We can check if data contains the ‘users’ key and then again retrieve values from data to count retrieved list length.

Before Python 3.8

if 'users' in data:    
 print(f'There are {len(data['users')} users!')
>> There are 2 users!

We can also store it in a variable to optimize dict search operations:

users = data.get('users', []) if users:    
print(f'There are {len(users)} users!') 
>> There are 2 users!

In Python 3.8 – with the walrus operator

if users := data.get('users', []):    
 print(f'There are {len(users)} users!')
>> There are 2 users! 

Much cleaner and simpler, right? It’s also useful when we have to do some complex calculations in any of the larger expressions.

Walrus in list comprehensions

Let’s generate some slugs (if possible) from some database objects in Django:

from django.utils.text import slugify 
from app.models import Product    

[slug for product in Product.objects.all() if slug := slugify(product.name)]

slugify may result in an empty string if the source string contains unsupported characters only (other than alphanumerics, underscore and hyphens). With such comprehension, we’ll get only possible slugs.

Yeah! Now we can hack a bit more with Python comprehensions.

2. Fast logging with the new f-string capabilities.

In every system, we need to store some logs during application lifetime. It’s nice to use Python 3 string formatting, cause it allows mixing string message with variable values and function results.

Let’s log some counter value with f-string:

print(f'Current counter equals {counter}') 
>> Current counter equals 11 

Still cool and consistent but let’s use new Python:

print(f'Current {counter=}') 
>> Current counter=11 

Extremely useful when we need to track variable values with their names. Every name refactoring will also automatically update our log messages!

We could also add some format specifiers that would convert our objects to a human-readable form:

readable form:
class Cat:  
  legs = 4  
  def __str__(self): 
    return f'I am a cat with {self.legs=}' 
object = Cat()  
print(f'Who are you? I am an {object=!s}')  
>> Who are you? I am an object=I am a cat with self.legs=4 

3. Reversed dict iteration

As we know, dicts became ordered by insertion in Python 3.6 for CPython implementation. We can use, standard dict just like OrderedDict. Now, with Python 3.8, we can also iterate over dicts in reversed order. Let’s take a look at the example:

states = {  
 'idle': { 'id': 1 }, 
 'processing': { 'id': 2 }, 
 'post-processing': { 'id': 3 }, 
 'finished': { 'id': 4 }
}  
print('States log:')  
for state in reversed(states):  
 print(f'{state} id: {states[state]["id"]}')  
>> States log:  
>> finished id: 4  
>> post-processing id: 3  
>> processing id: 2  
>> idle id: 1

Wrapping up Python 3.8 features

The three features that I selected from the new version of Python 3.8 bring many practical benefits in my opinion. I believe that with such an introduction you will be able to start using them right away. Warlus operators can simplify your complex logic. String formatting improvements also should allow you to write more consistent code. Reverse iteration and other CPython improvements and optimizations can be also very helpful.

Go ahead and give a try to Python 3.8!


Tomasz
Tomasz
Senior Software Engineering
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