Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

Emitted when using dict() to create a dictionary instead of a literal '{ ... }'. The literal is faster as it avoids an additional function call.

It is better to specify an encoding when opening documents. Using the system default implicitly can create problems on other operating systems. See https://peps.python.org/pep-0597/

It is better to specify an encoding when opening documents. Using the system default implicitly can create problems on other operating systems. See https://peps.python.org/pep-0597/

It is better to specify an encoding when opening documents. Using the system default implicitly can create problems on other operating systems. See https://peps.python.org/pep-0597/

If you use a naked except Exception: clause, you might end up catching exceptions other than the ones you expect to catch. This can hide bugs or make it harder to debug programs when unrelated errors are hidden.

It is better to specify an encoding when opening documents. Using the system default implicitly can create problems on other operating systems. See https://peps.python.org/pep-0597/

Used when a function call passes too few arguments.

Separate top-level function and class definitions with two blank lines.

Method definitions inside a class are separated by a single blank
line.

Extra blank lines may be used (sparingly) to separate groups of
related functions.  Blank lines may be omitted between a bunch of
related one-liners (e.g. a set of dummy implementations).

Use blank lines in functions, sparingly, to indicate logical
sections.

Okay: def a():\n    pass\n\n\ndef b():\n    pass
Okay: def a():\n    pass\n\n\nasync def b():\n    pass
Okay: def a():\n    pass\n\n\n# Foo\n# Bar\n\ndef b():\n    pass
Okay: default = 1\nfoo = 1
Okay: classify = 1\nfoo = 1

E301: class Foo:\n    b = 0\n    def bar():\n        pass
E302: def a():\n    pass\n\ndef b(n):\n    pass
E302: def a():\n    pass\n\nasync def b(n):\n    pass
E303: def a():\n    pass\n\n\n\ndef b(n):\n    pass
E303: def a():\n\n\n\n    pass
E304: @decorator\n\ndef a():\n    pass
E305: def a():\n    pass\na()
E306: def a():\n    def b():\n        pass\n    def c():\n        pass

Surround operators with a single space on either side.

- Always surround these binary operators with a single space on
  either side: assignment (=), augmented assignment (+=, -= etc.),
  comparisons (==, <, >, !=, <=, >=, in, not in, is, is not),
  Booleans (and, or, not).

- If operators with different priorities are used, consider adding
  whitespace around the operators with the lowest priorities.

Okay: i = i + 1
Okay: submitted += 1
Okay: x = x * 2 - 1
Okay: hypot2 = x * x + y * y
Okay: c = (a + b) * (a - b)
Okay: foo(bar, key='word', *args, **kwargs)
Okay: alpha[:-i]

E225: i=i+1
E225: submitted +=1
E225: x = x /2 - 1
E225: z = x **y
E225: z = 1and 1
E226: c = (a+b) * (a-b)
E226: hypot2 = x*x + y*y
E227: c = a|b
E228: msg = fmt%(errno, errmsg)

Surround operators with a single space on either side.

- Always surround these binary operators with a single space on
  either side: assignment (=), augmented assignment (+=, -= etc.),
  comparisons (==, <, >, !=, <=, >=, in, not in, is, is not),
  Booleans (and, or, not).

- If operators with different priorities are used, consider adding
  whitespace around the operators with the lowest priorities.

Okay: i = i + 1
Okay: submitted += 1
Okay: x = x * 2 - 1
Okay: hypot2 = x * x + y * y
Okay: c = (a + b) * (a - b)
Okay: foo(bar, key='word', *args, **kwargs)
Okay: alpha[:-i]

E225: i=i+1
E225: submitted +=1
E225: x = x /2 - 1
E225: z = x **y
E225: z = 1and 1
E226: c = (a+b) * (a-b)
E226: hypot2 = x*x + y*y
E227: c = a|b
E228: msg = fmt%(errno, errmsg)

Surround operators with a single space on either side.

- Always surround these binary operators with a single space on
  either side: assignment (=), augmented assignment (+=, -= etc.),
  comparisons (==, <, >, !=, <=, >=, in, not in, is, is not),
  Booleans (and, or, not).

- If operators with different priorities are used, consider adding
  whitespace around the operators with the lowest priorities.

Okay: i = i + 1
Okay: submitted += 1
Okay: x = x * 2 - 1
Okay: hypot2 = x * x + y * y
Okay: c = (a + b) * (a - b)
Okay: foo(bar, key='word', *args, **kwargs)
Okay: alpha[:-i]

E225: i=i+1
E225: submitted +=1
E225: x = x /2 - 1
E225: z = x **y
E225: z = 1and 1
E226: c = (a+b) * (a-b)
E226: hypot2 = x*x + y*y
E227: c = a|b
E228: msg = fmt%(errno, errmsg)

Surround operators with a single space on either side.

- Always surround these binary operators with a single space on
  either side: assignment (=), augmented assignment (+=, -= etc.),
  comparisons (==, <, >, !=, <=, >=, in, not in, is, is not),
  Booleans (and, or, not).

- If operators with different priorities are used, consider adding
  whitespace around the operators with the lowest priorities.

Okay: i = i + 1
Okay: submitted += 1
Okay: x = x * 2 - 1
Okay: hypot2 = x * x + y * y
Okay: c = (a + b) * (a - b)
Okay: foo(bar, key='word', *args, **kwargs)
Okay: alpha[:-i]

E225: i=i+1
E225: submitted +=1
E225: x = x /2 - 1
E225: z = x **y
E225: z = 1and 1
E226: c = (a+b) * (a-b)
E226: hypot2 = x*x + y*y
E227: c = a|b
E228: msg = fmt%(errno, errmsg)

Used when a function or method has no docstring. Some special methods like init do not require a docstring.

Used when a function or method has no docstring. Some special methods like init do not require a docstring.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.

Used when we detect a string that is being formatted with format() or % which could potentially be a f-string. The use of f-strings is preferred. Requires Python 3.6 and py-version >= 3.6.