Python Knowledge Base – Python Knowledge Base

Maintainability

• Ask for permission instead of forgiveness

• Avoid consecutive if-statements

• Avoid deprecated <> operator

• Avoid manually cloning a list

• Avoid “non-Pythonic” method names

• Avoid temporary kwargs

• Avoid using intermediate variables whenever possible

• Avoid using Java style dicts

• Avoid using len(x) to check if x is empty

• Avoid using “non-Pythonic” function names

• Avoid using “non-Pythonic” variable names

• Avoid using range() of len() to get index of iterable

• Avoid using the global statement

• Avoid using .update() to create merged dictionaries

• Avoid using wildcard (*) imports

• Consider documenting your class(es)

• Consider documenting your function(s)

• Consider simplifying bounds checks

• Consider simplifying out-of-bounds checks

• Consider splitting your assert statements

• Consider using ‘mpl’ as alias for matplotlib imports

• Consider using ‘np’ as alias for numpy imports

• Consider using ‘pd’ as alias for pandas imports

• Consider using ‘plt’ as alias for matplotlib.pyplot imports

• Consider using ‘sns’ as alias for seaborn imports

• Consider using ‘sp’ as alias for scipy imports

• dict.has_key() deprecated

• Double-check published secret key

• Module name not matching naming conventions

• object.__methods__ deprecated

• Prefer explicitly numbering replacement fields in a format string

• Prefer format() over % for string interpolation

• Try to start test methods with “test_”

• Use constants as default values for arguments

• Use dump instead of dumps for json files

• Use isinstance() to check for type

• Use load instead of loads for json files

• Use @property instead of Java-style of setter/getter methods

• Use tuple as 2nd argument of isinstance() to avoid repetition

• Use .update() instead of setting keys individually

• Using the global statement is unnecessary at module level

• .xreadlines() deprecated

Performance

• Avoid nested loop joins

• Avoid using C-style increment or decrement operators

• Consider an iterator instead of materializing the inner list

• Consider an iterator instead of materializing the list

• Consider literals instead of dict() constructor to initialize dictionaries

• Consider using a dict comprehension instead dict(...)

• Consider using a set comprehensions instead of passing a list to set()

• Prefer static methods over instance methods when possible

• Prefer with to open files

• Refactor expensive if-elif statement

• Remove unused module(s)

• Remove unused variable

• Use a set instead of a list() to find key

• Use extend() for list concatenation

Readability

• Avoid assigning a lambda expression to a variable

• Avoid inline comments

• Avoid None as a redundant second argument to dict.get()

• Avoid “non-Pythonic” attribute names

• Avoid “non-Pythonic” class names

• Avoid unnecessary name repetition in equality comparisions

• Avoid unnecessary parentheses after keyword

• Avoid unnecessary pass statements

• Clean up unused imports

• Consider using ‘dt’ as alias for datetime imports

• not ... is used instead of is not

• Omit len() as upper boundary

• Omit len() for indexing/slicing

• Prefer .format() over string concatenations via +

• Simplify repetetive unequal checks

• Test object identity with is or is not

• Use common abbreviations for libraries

• Use dict comprehension

• Use isinstance() instead of comparing types

• Use is or is not to compare with None

• Use .items() to iterate over a dictionary

• Use named tuples when returning more than one value from a function

• Use new raise syntax

• Use unpacking to update multiple values at once

• Use zip() to iterate over a pair of lists

Security

• Avoid using eval()

• Avoid using exec()

• Check published CONSUMER_SECRET

• Check published OAuth secret

• Check published OAuth token

• Check published Stripe API key

• Check usage of exploitable MD5 hashes

• Upgrade from md5 to hashlib

Frameworks

Django

• Access model manager through model class not instance

• Always define __str__ or __unicode__ for each model

• Avoid directly altering custom many-to-many relationships

• Avoid importing from django.db.models.fields

• Avoid null=True on string fields

• Avoid overwriting init method of model classes

• Avoid two consecutive underscores in field name

• Avoid using len() with RawQuerySet

• Avoid using locals() to populate view context

• Avoid using RawQuerySet as boolean value

• Call super() when overwriting unittest methods

• Check identical value for SERVER_EMAIL and DEFAULT_FROM_EMAIL

• Define get_absolute_url whenever possible

• Directly accessing INSTALLED_APPS

• Do not interact with database within ready()

• Do not override field attributes in child model

• Don’t pass args and kwargs to reverse()

• Don’t use joins with update()

• Don’t use same path for MEDIA_ROOT and STATIC_ROOT

• Don’t use same path for MEDIA_URL and STATIC_URL

• Don’t use string formatting on raw queries

• Don’t use unsupported arguments on FileField

• Double-check published secret key

• Duplicate application names

• Ensure indexes on your Django models

• Inherit proxy models from non-proxy parent

• Invalid import from django.conf.settings

• Leverage queryset cache as much as possible

• Missing required field in settings

• Model attribute overwrites method definition

• Place database manipulations in try-except blocks

• Remove redundant import of global_settings

• SECURE_PROXY_SSL_HEADER set

• Set ALLOWED_HOSTS when DEBUG=False

• Try to start test methods with “test_”

• Use a NullBooleanField

• Use django.conf.urls.url() instances for urlpatterns

• Use django.test.TestCase when accessing the database

• Use forward slashes in settings

• Use getobjector_404() instead of catching ObjectDoesNotExist

• Use model class as first argument for field type

• Use reverse() instead of hard-coded URL

• Use settings() method instead of manipulating settings directly

• Using BinaryField to store raw binary data

Flask

• Avoid two consecutive underscores in column name

• Consider using url_prefix for views with similar routes

• Define SERVER_NAME when using sub domains

• Define url_prefix or subdomain during blueprint registration

• Prevent SQL injections by avoiding string interpolations

• route should be the outermost decorator

• Use converter for type checking url variables

• Use relative imports

Plone

• Catching ImportError to detect package availability

• Comma-separated imports

• Prefer explicitly numbering replacement fields in a format string

• Refactor deprecated unittest aliases

• Using request.AUTHENTICATED_USER

Odoo

• Avoid calling magic methods

• Avoid None as a redundant second argument to dict.get()

• Avoid temporary kwargs

• Avoid using intermediate variables whenever possible

• Avoid using Java style dicts

• Avoid using len(x) to check if x is empty

• Avoid using .update() to create merged dictionaries

• dict.has_key() deprecated

• Odoo model defaults require four parameters

• Use constants and avoid magic numbers

• Use isinstance() to check for type

• Use tuple as 2nd argument of isinstance() to avoid repetition

• Use .update() instead of setting keys individually