vulture 1.2

Find dead code

Vulture - Find dead code

Vulture finds unused code in Python programs. This is useful for cleaning up and finding errors in large code bases. If you run Vulture on both your library and test suite you can find untested code.

Due to Python’s dynamic nature, static code analyzers like Vulture are likely to miss some dead code. Also, code that is only called implicitly may be reported as unused. Nonetheless, Vulture can be a very helpful tool for higher code quality.

Features

• fast: uses static code analysis

• tested: tests itself and has complete test coverage

• complements pyflakes and has the same output syntax

• sorts unused classes and functions by size with --sort-by-size

• supports Python 2.7 and Python >= 3.5

Installation

$ pip install vulture  # from PyPI
$ pip install .        # from cloned repo

Usage

$ vulture myscript.py  # or
$ python3 -m vulture myscript.py
$ vulture myscript.py mypackage/
$ vulture myscript.py --min-confidence 100  # Only report 100% dead code.

The provided arguments may be Python files or directories. For each directory Vulture analyzes all contained *.py files.

Vulture assigns each chunk of dead code a confidence value. A confidence value of 100% means that the code will never be executed. Values below 100% are only estimates for how likely it is that the code is unused.

After you have found and deleted dead code, run Vulture again, because it may discover more dead code.

Handling false positives

You can add used code that is reported as unused to a Python module and add it to the list of scanned paths. To obtain such a whitelist automatically, pass --make-whitelist to Vulture.

$ vulture mydir --make-whitelist > whitelist.py
$ vulture mydir whitelist.py

We collect whitelists for common Python modules and packages in vulture/whitelists/ (pull requests are welcome). If you want to ignore a whole file or directory, use the --exclude parameter (e.g., --exclude *settings.py,docs/).

Ignoring names

You can use --ignore-names foo*,ba[rz] to let Vulture ignore all names starting with foo and the names bar and baz. Additionally, the --ignore-decorators option can be used to ignore functions decorated with the given decorator. This is helpful for example in Flask projects, where you can use --ignore-decorators "@app.route" to ignore all functions with the @app.route decorator.

We recommend using whitelists instead of --ignore-names or --ignore-decorators whenever possible, since whitelists are automatically checked for syntactic correctness when passed to Vulture and often you can even pass them to your Python interpreter and let it check that all whitelisted code actually still exists in your project.

Marking unused variables

There are situations where you can’t just remove unused variables, e.g., in tuple assignments or function signatures. Vulture will ignore these variables if they start with an underscore (e.g., _x, y = get_pos()).

Minimum confidence

You can use the --min-confidence flag to set the minimum confidence for code to be reported as unused. Use --min-confidence 100 to only report code that is guaranteed to be unused within the analyzed files.

How does it work?

Vulture uses the ast module to build abstract syntax trees for all given files. While traversing all syntax trees it records the names of defined and used objects. Afterwards, it reports the objects which have been defined, but not used. This analysis ignores scopes and only takes object names into account.

Vulture also detects unreachable code by looking for code after return, break, continue and raise statements, and by searching for unsatisfiable if- and while-conditions.

Sort by size

When using the --sort-by-size option, Vulture sorts unused code by its number of lines. This helps developers prioritize where to look for dead code first.

Examples

Consider the following Python script (dead_code.py):

import os

class Greeter:
    def greet(self):
        print("Hi")

def hello_world():
    message = "Hello, world!"
    greeter = Greeter()
    greet_func = getattr(greeter, "greet")
    greet_func()

if __name__ == "__main__":
    hello_world()

Calling

vulture dead_code.py

results in the following output:

dead_code.py:1: unused import 'os' (90% confidence)
dead_code.py:4: unused function 'greet' (60% confidence)
dead_code.py:8: unused variable 'message' (60% confidence)

Vulture correctly reports “os” and “message” as unused, but it fails to detect that “greet” is actually used. The recommended method to deal with false positives like this is to create a whitelist Python file.

Preparing whitelists

In a whitelist we simulate the usage of variables, attributes, etc. For the program above, a whitelist could look as follows:

# whitelist_dead_code.py
from dead_code import Greeter
Greeter.greet

Alternatively, you can pass --make-whitelist to Vulture and obtain an automatically generated whitelist.

Passing both the original program and the whitelist to Vulture

vulture dead_code.py whitelist_dead_code.py

makes Vulture ignore the “greet” method:

dead_code.py:1: unused import 'os' (90% confidence)
dead_code.py:8: unused variable 'message' (60% confidence)

Exit codes

Exit code	Description
0	No dead code found
1	Dead code found
1	Invalid input (file missing, syntax error, wrong encoding)
2	Invalid command line arguments

Similar programs

• pyflakes finds unused imports and unused local variables (in addition to many other programmatic errors).

• coverage finds unused code more reliably than Vulture, but requires all branches of the code to actually be run.

• uncalled finds dead code by using the abstract syntax tree (like Vulture), regular expressions, or both.

• dead finds dead code by using the abstract syntax tree (like Vulture).

Participate

Please visit https://github.com/jendrikseipp/vulture to report any issues or to make pull requests.

• Contributing guide: CONTRIBUTING.rst

• Changelog: NEWS.rst

• Roadmap: TODO.rst

News

1.2 (2019-11-22)

• Fix tests for Python 3.8 (#166).

• Use new Constant AST node under Python 3.8+ (#175).

• Add test for f-strings (#177).

• Add whitelist for logging module.

1.1 (2019-09-23)

• Add sys.excepthook to sys whitelist.

• Add whitelist for ctypes module.

• Check that type annotations are parsed and type comments are ignored (thanks @kx-chen).

• Support checking files with BOM under Python 2.7 (#170).

1.0 (2018-10-23)

• Add --ignore-decorators flag (thanks @RJ722).

• Add whitelist for threading module (thanks @andrewhalle).

0.29 (2018-07-31)

• Add --ignore-names flag for ignoring names matching the given glob patterns (thanks @RJ722).

0.28 (2018-07-05)

• Add --make-whitelist flag for reporting output in whitelist format (thanks @RJ722).

• Ignore case of --exclude arguments on Windows.

• Add *-test.py to recognized test file patterns.

• Add failureException, longMessage and maxDiff to unittest whitelist.

• Refer to actual objects rather than their mocks in default whitelists (thanks @RJ722).

• Don’t import any Vulture modules in setup.py (thanks @RJ722).

0.27 (2018-06-05)

• Report while (True): ... else: ... as unreachable (thanks @RJ722).

• Use argparse instead of optparse.

• Whitelist Mock.return_value and Mock.side_effect in unittest.mock module.

• Drop support for Python 2.6 and 3.3.

• Improve documentation and test coverage (thanks @RJ722).

0.26 (2017-08-28)

• Detect async function definitions (thanks @RJ722).

• Add Item.get_report() method (thanks @RJ722).

• Move method for finding Python modules out of Vulture class.

0.25 (2017-08-15)

• Detect unsatisfiable statements containing and, or and not.

• Use filenames and line numbers as tie-breakers when sorting by size.

• Store first and last line numbers in Item objects.

• Pass relevant options directly to scavenge() and report().

0.24 (2017-08-14)

• Detect unsatisfiable while-conditions (thanks @RJ722).

• Detect unsatisfiable if- and else-conditions (thanks @RJ722).

• Handle null bytes in source code.

0.23 (2017-08-10)

• Add --min-confidence flag (thanks @RJ722).

0.22 (2017-08-04)

• Detect unreachable code after return, break, continue and raise (thanks @RJ722).

• Parse all variable and attribute names in new format strings.

• Extend ast whitelist.

0.21 (2017-07-26)

• If an unused item is defined multiple times, report it multiple times.

• Make size estimates for function calls more accurate.

• Create wheel files for Vulture (thanks @RJ722).

0.20 (2017-07-26)

• Report unused tuple assignments as dead code.

• Report attribute names that have the same names as variables as dead code.

• Let Item class inherit from object (thanks @RJ722).

• Handle names imported as aliases like all other used variable names.

• Rename Vulture.used_vars to Vulture.used_names.

• Use function for determining which imports to ignore.

• Only try to import each whitelist file once.

• Store used names and used attributes in sets instead of lists.

• Fix estimating the size of code containing ellipses (…).

• Refactor and simplify code.

0.19 (2017-07-20)

• Don’t ignore __foo variable names.

• Use separate methods for determining whether to ignore classes and functions.

• Only try to find a whitelist for each defined import once (thanks @roivanov).

• Fix finding the last child for many types of AST nodes.

0.18 (2017-07-17)

• Make –sort-by-size faster and more accurate (thanks @RJ722).

0.17 (2017-07-17)

• Add get_unused_code() method.

• Return with exit code 1 when syntax errors are found or files can’t be read.

0.16 (2017-07-12)

• Differentiate between unused classes and functions (thanks @RJ722).

• Add –sort-by-size option (thanks @jackric and @RJ722).

• Count imports as used if they are accessed as module attributes.

0.15 (2017-07-04)

• Automatically include whitelists based on imported modules (thanks @RJ722).

• Add –version parameter (thanks @RJ722).

• Add appveyor tests for testing on Windows (thanks @RJ722).

0.14 (2017-04-06)

• Add stub whitelist file for Python standard library (thanks @RJ722)

• Ignore class names starting with “Test” in “test_” files (thanks @thisch).

• Ignore “test_” functions only in “test_” files.

0.13 (2017-03-06)

• Ignore star-imported names since we cannot detect whether they are used.

• Move repository to GitHub.

0.12 (2017-01-05)

• Detect unused imports.

• Use tokenize.open() on Python >= 3.2 for reading input files, assume UTF-8 encoding on older Python versions.

0.11 (2016-11-27)

• Use the system’s default encoding when reading files.

• Report syntax errors instead of aborting.

0.10 (2016-07-14)

• Detect unused function and method arguments (issue #15).

• Detect unused *args and **kwargs parameters.

• Change license from GPL to MIT.

0.9 (2016-06-29)

• Don’t flag attributes as unused if they are used as global variables in another module (thanks Florian Bruhin).

• Don’t consider “True” and “False” variable names.

• Abort with error message when invoked on .pyc files.

0.8.1 (2015-09-28)

• Fix code for Python 3.

0.8 (2015-09-28)

• Do not flag names imported with “import as” as dead code (thanks Tom Terrace).

0.7 (2015-09-26)

• Exit with exitcode 1 if path on commandline can’t be found.

• Test vulture with vulture using a whitelist module for false positives.

• Add tests that run vulture as a script.

• Add “python setup.py test” command for running tests.

• Add support for tox.

• Raise test coverage to 100%.

• Remove ez_setup.py.

0.6 (2014-09-06)

• Ignore function names starting with “test_”.

• Parse variable names in new format strings (e.g. “This is {x}”.format(x=”nice”)).

• Only parse alphanumeric variable names in format strings and ignore types.

• Abort with exit code 1 on syntax errors.

• Support installation under Windows by using setuptools (thanks Reuben Fletcher-Costin).

0.5 (2014-05-09)

• If dead code is found, exit with 1.

0.4.1 (2013-09-17)

• Only warn if a path given on the command line cannot be found.

0.4 (2013-06-23)

• Ignore unused variables starting with an underscore.

• Show warning for syntax errors instead of aborting directly.

• Print warning if a file cannot be found.

0.3 (2012-03-19)

• Add support for python3

• Report unused attributes

• Find tuple assignments in comprehensions

• Scan files given on the command line even if they don’t end with .py

0.2 (2012-03-18)

• Only format nodes in verbose mode (gives 4x speedup).

0.1 (2012-03-17)

• First release.