Coding Style

To contribute code to the project, you must diligently follow the style rules describe in this chapter. Having a clean and structured code is very important for our development lifecycle, and not compliant code will most likely be rejected.

Essentially CAPE’s code style is based on PEP 8 - Style Guide for Python Code and PEP 257 – Docstring Conventions.



The code must have a 4-spaces-tabs indentation. Since Python enforces the indentation, make sure to configure your editor properly or your code might cause malfunctioning.

Maximum Line Length

Limit all lines to a maximum of 132 characters.

Blank Lines

Separate the class definition and the top-level function with one blank line. Methods definitions inside a class are separated by a single blank line:

class MyClass:
    """Doing something."""

    def __init__(self):

    def do_it(self, what):
        """Do it.
        @param what: do what.

Use blank lines in functions, sparingly, to isolate logic sections. Import blocks are separated by a single blank line, import blocks are separated from classes by one blank line.


Imports must be on separate lines. If you’re importing multiple objects from a package, use a single line:

from lib import a, b, c


from lib import a
from lib import b
from lib import c

Always specify explicitly the objects to import:

from lib import a, b, c


from lib import *


Strings must be delimited by double quotes (“).

Printing and Logging

We discourage the use of print(): if you need to log an event please use Python’s logging which is already initialized by CAPE.

In your module add:

import logging
log = logging.getLogger(__name__)

And use the log handle, for more details refer to the Python documentation.

In case you need to print a string to standard output, use the print() function:


NOT the statement:

print "foo"

Checking for keys in data structures

When checking for a key in a data structure, use the clause “in” for example:

if "bar" in foo:


Custom exceptions must be defined in the lib/cuckoo/common/ file or the local module if the exception should not be global.

The following is the current CAPE exceptions chain:

.-- CuckooCriticalError
|   |-- CuckooStartupError
|   |-- CuckooDatabaseError
|   |-- CuckooMachineError
|   `-- CuckooDependencyError
|-- CuckooOperationalError
|   |-- CuckooAnalysisError
|   |-- CuckooProcessingError
|   `-- CuckooReportError
`-- CuckooGuestError

Beware that the use of CuckooCriticalError and its child exceptions will cause CAPE to terminate.


Custom exception names must start with “Cuckoo” and end with “Error” if it represents an unexpected malfunction.

Exception handling

When catching an exception and accessing its handle, use as e:

except Exception as e:


except Exception, something:

It’s a good practice to use “e” instead of “e.message”.


All code must be documented in docstring format, see PEP 257 – Docstring Conventions. Additional comments may be added in logical blocks to make the code easier to understand.

Automated testing

We believe in automated testing to provide high-quality code and avoid dumb bugs. When possible, all code must be committed with proper unit tests. Particular attention must be placed when fixing bugs: it’s good practice to write unit tests to reproduce the bug. All unit tests and fixtures are placed in the tests folder in the CAPE root. We adopted Nose as the unit testing framework.

Poetry and pre-commit hooks

After cloning the git repository, the first commands that you should do: `bash poetry install poetry run pre-commit install ` This will install the pre-commit hooks, ensuring that all files have to conform to black and isort.