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

Used when a function or method takes too many arguments.

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

Used when a class inherit from object, which under python3 is implicit, hence can be safely removed from bases.

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

Emitted when calling the super() builtin with the current class and instance. On Python 3 these arguments are the default and they can be omitted.

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

Used when pylint has been unable to import a module.

Used when a warning note as FIXME or XXX is detected.

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 46.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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)

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)

Avoid breaks after binary operators.

The preferred place to break around a binary operator is before the
operator, not after it.

W504: (width == 0 +\n height == 0)
W504: (width == 0 and\n height == 0)
W504: var = (1 &\n       ~2)

Okay: foo(\n    -x)
Okay: foo(x\n    [])
Okay: x = '''\n''' + ''
Okay: x = '' + '''\n'''
Okay: foo(x,\n    -y)
Okay: foo(x,  # comment\n    -y)

The following should be W504 but unary_context is tricky with these
Okay: var = (1 /\n       -2)
Okay: var = (1 +\n       -1 +\n       -2)

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

Used when the name doesn't conform to naming rules associated to its type (constant, variable, class...).

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

Used when the name doesn't conform to naming rules associated to its type (constant, variable, class...).