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Code Styling

Not using setdefault() to initialize a dictionary

When initializing a dictionary, it is common to see a code check for the existence of a key and then create the key if it does not exist.

Given a dictionary = {}, if you want to create a key if it doesn't exist, instead of doing:

except KeyError:
    dictionary['key'] = {}

You can use:

dictionary.setdefault('key', {})

Black code style

Black is a style guide enforcement tool.


Flake8 is another style guide enforcement tool.


f-strings, also known as formatted string literals, are strings that have an f at the beginning and curly braces containing expressions that will be replaced with their values.

Introduced in Python 3.6, they are more readable, concise, and less prone to error than other ways of formatting, as well as faster.

>>> name = "Eric"
>>> age = 74
>>> f"Hello, {name}. You are {age}."
'Hello, Eric. You are 74.'

Arbitrary expressions

Because f-strings are evaluated at runtime, you can put any valid Python expressions in them. For example, calling a function or method from within.

>>> f"{name.lower()} is funny."
'eric idle is funny.'

Multiline f-strings

>>> name = "Eric"
>>> profession = "comedian"
>>> affiliation = "Monty Python"
>>> message = (
...     f"Hi {name}. "
...     f"You are a {profession}. "
...     f"You were in {affiliation}."
... )
>>> message
'Hi Eric. You are a comedian. You were in Monty Python.'

Lint error fixes and ignores

Fix Pylint R0201 error

The error shows Method could be a function, it is used when there is no reference to the class, suggesting that the method could be used as a static function instead.

Attempt using either of the decorators @classmethod or @staticmethod.

If you don't need to change or use the class methods, use staticmethod.


Class Foo(object):
    def bar(self, baz):
        return llama

Try instead to use:

Class Foo(object):
    def bar(cls, baz):
        return llama


Class Foo(object):
    def bar(baz):
        return llama

W1203 with F-strings

This rule suggest you to use the % interpolation in the logging methods because it might save some interpolation time when a logging statement is not run. Nevertheless the performance improvement is negligible and the advantages of using f-strings far outweigh them.

W0106 in list comprehension

They just don't support it they suggest to use normal for loops.

W1514 set encoding on open

with open('file.txt', 'r', encoding='utf-8'):

[SIM105 Use


To bypass exceptions, it's better to use:

from contextlib import suppress

with suppress(FileNotFoundError):

Instead of:

except FileNotFoundError:

Last update: 2022-03-10