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.
--sort-by-size$ pip install vulture
$ 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.
After you have found and deleted dead code, run Vulture again, because it may discover more dead code.
In addition to finding unused functions, classes, etc., Vulture can detect unreachable code. Each chunk of dead code is assigned a confidence value between 60% and 100%, where a value of 100% signals that it is certain that the code won't be executed. Values below 100% are very rough estimates (based on the type of code chunk) for how likely it is that the code is unused.
| Code type | Confidence value |
|---|---|
| function/method/class argument, unreachable code | 100% |
| import | 90% |
| attribute, class, function, method, property, variable | 60% |
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.
When Vulture incorrectly reports chunks of code as unused, you have several options for suppressing the false positives. If fixing your false positives could benefit other users as well, please file an issue report.
The recommended option is to 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
Note that the resulting whitelist.py file will contain valid Python
syntax, but for Python to be able to run it, you will usually have to
make some modifications.
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/*.py,*/test_*.py,*/.venv/*.py"). The
exclude patterns are matched against absolute paths.
For compatibility with flake8, Vulture
supports the F401 and
F841 error
codes for ignoring unused imports (# noqa: F401) and unused local
variables (# noqa: F841). However, we recommend using whitelists instead
of noqa comments, since noqa comments add visual noise to the code and
make it harder to read.
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 the names of functions
decorated with the given decorator (but not their arguments or function body).
This is helpful for example in Flask
projects, where you can use --ignore-decorators "@app.route" to ignore all
function names with the @app.route decorator. Note that Vulture simplifies
decorators it cannot parse: @foo.bar(x, y) becomes "@foo.bar" and
@foo.bar(x, y).baz becomes "@" internally.
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.
There are situations where you can't just remove unused variables, e.g.,
in function signatures. The recommended solution is to use the del
keyword as described in the
PyLint manual and on
StackOverflow:
def foo(x, y):
del y
return x + 3
Vulture will also ignore all variables that start with an underscore, so
you can use _x, y = get_pos() to mark unused tuple assignments or
function arguments, e.g., def foo(x, _y).
Raise the minimum confidence value with the --min-confidence flag.
If Vulture complains about code like if False:, you can use a Boolean
flag debug = False and write if debug: instead. This makes the code
more readable and silences Vulture.
See #216. For
example, instead of def foo(arg: "Sequence"): ..., we recommend using
from __future__ import annotations
def foo(arg: Sequence):
...
You can also store command line arguments in pyproject.toml under the
tool.vulture section. Simply remove leading dashes and replace all
remaining dashes with underscores.
Options given on the command line have precedence over options in
pyproject.toml.
Example Config:
[tool.vulture]
exclude = ["*file*.py", "dir/"]
ignore_decorators = ["@app.route", "@require_*"]
ignore_names = ["visit_*", "do_*"]
make_whitelist = true
min_confidence = 80
paths = ["myscript.py", "mydir", "whitelist.py"]
sort_by_size = true
verbose = true
Vulture will automatically look for a pyproject.toml in the current working directory.
To use a pyproject.toml in another directory, you can use the --config path/to/pyproject.toml flag.
You can use a pre-commit hook to run
Vulture before each commit. For this, install pre-commit and add the
following to the .pre-commit-config.yaml file in your repository:
repos:
- repo: https://github.com/jendrikseipp/vulture
rev: 'v2.3' # or any later Vulture version
hooks:
- id: vulture
Then run pre-commit install. Finally, create a pyproject.toml file
in your repository and specify all files that Vulture should check under
[tool.vulture] --> paths (see above).
There's also a GitHub Action for Vulture and you can use Vulture programatically. For example:
import vulture
v = vulture.Vulture()
v.scavenge(['.'])
unused_code = v.get_unused_code() # returns a list of `Item` objects
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.
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.
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()
func_name = "greet"
greet_func = getattr(greeter, func_name)
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 code | Description |
|---|---|
| 0 | No dead code found |
| 1 | Invalid input (file missing, syntax error, wrong encoding) |
| 2 | Invalid command line arguments |
| 3 | Dead code found |
Please visit https://github.com/jendrikseipp/vulture to report any issues or to make pull requests.
get_unused_code and the fields of the Item class (John Doknjas, #361).tests/**/*.toml in sdist (Colin Watson).ruff for linting and formatting (Anh Trinh, #347, #349).tox by pre-commit for linting and formatting (Anh Trinh, #349).--config flag to specify path to pyproject.toml configuration file (Glen Robertson, #352).MagicMock and Mock (maxrake, #342).end_lineno AST attribute to obtain more accurate line counts (Jendrik Seipp).--help and --version again (Jendrik Seipp, #321).UnicodeEncodeError exception handling to core.py (milanbalazs, #299).Enum attributes _name_ and _value_ (Eugene Toder, #305).setup_module(), teardown_module(), etc. in pytest test_*.py files (Jendrik Seipp).socketserver.TCPServer.allow_reuse_address (Ben Elliston).--exclude patterns are matched against absolute paths (Jendrik Seipp, #260).match statement support (kreathon, #276, #291).__all__ as used (kreathon, #172, #282).pint.UnitRegistry.default_formatter (Ben Elliston, #258).del keyword to mark unused variables (sshishov, #279).locals() (jingw, #225).getattr/hasattr(obj, "constant_string", ...) as a reference to
obj.constant_string (jingw, #219).x.some_name but reading via
some_name, at the cost of potential false negatives (jingw, #221).pyproject.toml (Michel Albert, #164, #215).# type: ... comments if on Python 3.8+ (jingw, #220).test or tests directories test files
(Jendrik Seipp).logging.Logger.propagate attribute (Jendrik Seipp).__init__.py (RJ722, #192).string.Formatter (Joseph Bylund, #183).Constant AST node under Python 3.8+ (#175).logging module.sys.excepthook to sys whitelist.ctypes module.--ignore-decorators flag (thanks @RJ722).threading module (thanks @andrewhalle).--ignore-names flag for ignoring names matching the given glob
patterns (thanks @RJ722).--make-whitelist flag for reporting output in whitelist format
(thanks @RJ722).--exclude arguments on Windows.*-test.py to recognized test file patterns.failureException, longMessage and maxDiff to unittest
whitelist.while (True): ... else: ... as unreachable (thanks @RJ722).argparse instead of optparse.async function definitions (thanks @RJ722).Item.get_report() method (thanks @RJ722).and, or and not.scavenge() and report().while-conditions (thanks @RJ722).if- and else-conditions (thanks @RJ722).--min-confidence flag (thanks @RJ722).return, break, continue and
raise (thanks @RJ722).object (thanks @RJ722).FAQs
Find dead code
We found that vulture demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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