A tool for refurbishing and modernizing Python codebases.
# main.py
for filename in ["file1.txt", "file2.txt"]:
with open(filename) as f:
contents = f.read()
lines = contents.splitlines()
for line in lines:
if not line or line.startswith("# ") or line.startswith("// "):
continue
for word in line.split():
print(f"[{word}]", end="")
print("")Running:
$ refurb main.py
main.py:3:17 [FURB109]: Use `in (x, y, z)` instead of `in [x, y, z]`
main.py:4:5 [FURB101]: Use `y = Path(x).read_text()` instead of `with open(x, ...) as f: y = f.read()`
main.py:10:40 [FURB102]: Replace `x.startswith(y) or x.startswith(z)` with `x.startswith((y, z))`
main.py:16:9 [FURB105]: Use `print() instead of `print("")`
$ pipx install refurb
$ refurb file.py folder/
Note Refurb must be run on Python 3.10+, though it can check Python 3.7+ code by setting the
--python-versionflag.
You can use refurb --explain FURB123, where FURB123 is the error code you are trying to look up.
For example:
$ refurb --explain FURB123
Don't cast a variable or literal if it is already of that type. For
example:
Bad:
```
name = str("bob")
num = int(123)
```
Good:
```
name = "bob"
num = 123
```
An online list of all available checks can be viewed here.
Use --ignore 123 to ignore error 123. The error code can be in the form FURB123 or 123.
This flag can be repeated.
The
FURBprefix indicates that this is a built-in error. TheFURBprefix is optional, but for all other errors (ie,ABC123), the prefix is required.
You can also use inline comments to disable errors:
x = int(0) # noqa: FURB123
y = list() # noqaHere, noqa: FURB123 specifically ignores the FURB123 error for that line, and noqa ignores
all errors on that line.
You can also specify multiple errors to ignore by separating them with a comma/space:
x = not not int(0) # noqa: FURB114, FURB123
x = not not int(0) # noqa: FURB114 FURB123Certain checks are disabled by default, and need to be enabled first. You can do this using the
--enable ERR flag, where ERR is the error code of the check you want to enable. A disabled
check differs from an ignored check in that a disabled check will never be loaded, whereas an
ignored check will be loaded, an error will be emitted, and the error will be suppressed.
Use the --verbose/-v flag to get a full list of enabled checks.
The opposite of --enable is --disable, which will disable a check. When --enable and --disable
are both specified via the command line, whichever one comes last will take precedence. When using
enable and disable via the config file, disable will always take precedence.
Use the --disable-all flag to disable all checks. This allows you to incrementally --enable checks
as you see fit, as opposed to adding a bunch of --ignore flags. To use this in the config file,
set disable_all to true.
Use the --enable-all flag to enable all checks by default. This allows you to opt into all checks
that Refurb (and Refurb plugins) have to offer. This is a good option for new codebases. To use this
in a config file, set enable_all to true.
In the config file, disable_all/enable_all is applied first, and then the enable and disable
fields are applied afterwards.
Note that
disable_allandenable_allare mutually exclusive, both on the command line and in the config file. You will get an error if you try to specify both.
You can also disable checks by category using the #category syntax. For example, --disable "#readability"
will disable all checks with the readability category. The same applies for enable and ignore.
Also, if you disable an entire category you can still explicitly re-enable a check in that category.
Note that
#readabilityis wrapped in quotes because your shell will interpret the#as the start of a comment.
Use the --python-version flag to tell Refurb which version of Python your codebase is using. This
should allow for better detection of language features, and allow for better error messages. The argument
for this flag must be in the form x.y, for example, 3.10.
The syntax for using this in the config file is python_version = "3.10".
When the Python version is unspecified, Refurb uses whatever version your local Python installation uses.
For example, if your python --version is 3.11.5, Refurb uses 3.11, dropping the 5 patch version.
By default everything is outputted as plain text:
file.py:1:5 [FURB123]: Replace `int(x)` with `x`
Here are all of the available formats:
text: The defaultgithub: Print output for use with GitHub Annotations- More to come!
To change the default format use --format XYZ on the command line, or format = "XYZ" in the config file.
By default errors are sorted by filename, then by error code. To change this, use the --sort XYZ flag on
the command line, or sort_by = "XYZ" in the config file, where XYZ is one of the following sort modes:
filename: Sort files in alphabetical order (the default)error: Sort by error first, then by filename
This is typically used for development purposes, but can also be used to better fine-tune Mypy from
within Refurb. Any command line arguments after -- are passed to Mypy. For example:
$ refurb files -- --show-traceback
This tells Mypy to show a traceback if it crashes.
You can also use this in the config file by assigning an array of values to the mypy_args field.
Note that any Mypy arguments passed via the command line arguments will override the mypy_args
field in the config file.
In addition to the command line arguments, you can also add your settings in the pyproject.toml file.
For example, the following command line arguments:
refurb file.py --ignore 100 --load some_module --quiet
Corresponds to the following in your pyproject.toml file:
[tool.refurb]
ignore = [100]
load = ["some_module"]
quiet = trueNow all you need to type is refurb file.py!
Note that the values in the config file will be merged with the values specified via the
command line. In the case of boolean arguments like --quiet, the command line arguments
take precedence. All other arguments (such as ignore and load) will be combined.
You can use the --config-file flag to tell Refurb to use a different config file from the
default pyproject.toml file. Note that it still must be in the same form as the normal
pyproject.toml file.
Click here to see some example config files.
If you have a large codebase you might want to ignore errors for certain files or folders,
which allows you to incrementally fix errors as you see fit. To do that, add the following
to your pyproject.toml file:
# these settings will be applied globally
[tool.refurb]
enable_all = true
# these will only be applied to the "src" folder
[[tool.refurb.amend]]
path = "src"
ignore = ["FURB123", "FURB120"]
# these will only be applied to the "src/util.py" file
[[tool.refurb.amend]]
path = "src/util.py"
ignore = ["FURB125", "FURB148"]Note that only the
ignorefield is available in theamendsections. This is because a check can only be enabled/disabled for the entire codebase, and cannot be selectively enabled/disabled on a per-file basis. Assuming a check is enabled though, you can simplyignorethe errors for the files of your choosing.
You can use Refurb with pre-commit by adding the following
to your .pre-commit-config.yaml file:
- repo: https://github.com/dosisod/refurb
rev: REVISION
hooks:
- id: refurbReplacing REVISION with a version or SHA of your choosing (or leave it blank to
let pre-commit find the most recent one for you).
Installing plugins for Refurb is very easy:
$ pip install refurb-plugin-example
Where refurb-plugin-example is the name of the plugin. Refurb will automatically load
any installed plugins.
To make your own Refurb plugin, see the refurb-plugin-example repository
for more info.
If you want to extend Refurb but don't want to make a full-fledged plugin,
you can easily create a one-off check file with the refurb gen command.
Note that this command uses the
fzffuzzy-finder for getting user input, so you will need to install fzf before continuing.
Here is the basic overview for creating a new check using the refurb gen command:
- First select the node type you want to accept
- Then type in where you want to save the auto generated file
- Add your code to the new file
To get an idea of what you need to add to your check, use the --debug flag to see the
AST representation for a given file (ie, refurb --debug file.py). Take a look at the
files in the refurb/checks/ folder for some examples.
Then, to load your new check, use refurb file.py --load your.path.here
Note that when using
--load, you need to use dots in your argument, just like importing a normal python module. Ifyour.path.hereis a directory, all checks in that directory will be loaded. If it is a file, only that file will be loaded.
If Refurb is running slow, use the --timing-stats flag to diagnose why:
$ refurb file --timing-stats /tmp/stats.json
This will output a JSON file with the following information:
- Total time Mypy took to parse the modules (a majority of the time usually).
- Time Mypy spent parsing each module. Useful for finding very large/unused files.
- Time Refurb spent checking each module. These numbers should be very small (less than 100ms).
Larger files naturally take longer to check, but files that take way too long should be looked into, as an issue might only manifest themselves when a file reaches a certain size.
Color output is enabled by default in Refurb. To disable it, do one of the following:
-
Set the
NO_COLORenv var. -
Use the
--no-colorflag. -
Set
color = falsein the config file. -
Pipe/redirect Refurb output to another program or file.
To setup locally run:
$ git clone https://github.com/dosisod/refurb
$ cd refurb
$ make install
Tests can be ran all at once using make, or you can run each tool on its own using
make black, make flake8, and so on.
Unit tests can be ran with pytest or make test.
Since the end-to-end (e2e) tests are slow, they are not ran when running
make. You will need to runmake test-e2eto run them.
We encourage people to update the documentation when they see typos and other issues!
With that in mind though, don't directly modify the docs/checks.md file. It is auto-generated
and will be overridden when new checks are added. The documentation for checks can be updated
by changing the docstrings of in the checks themselves. For example, to update FURB100,
change the docstring of the ErrorInfo class in the refurb/checks/pathlib/with_suffix.py file.
You can find the file for a given check by grep-ing for code = XYZ, where XYZ is the check
you are looking for but with the FURB prefix removed.
Use the --verbose flag with --explain to find the filename for a given check. For example:
$ refurb --explain FURB123 --verbose
Filename: refurb/checks/readability/no_unnecessary_cast.py
FURB123: no-redundant-cast [readability]
...
I love doing code reviews: I like taking something and making it better, faster, more elegant, and so on. Lots of static analysis tools already exist, but none of them seem to be focused on making code more elegant, more readable, or more modern. That is where Refurb comes in.
Refurb is heavily inspired by clippy, the built-in linter for Rust.
Refurb is not a style/type checker. It is not meant as a first-line of defense for linting and finding bugs, it is meant for making good code even better.
There are already lots of tools out there for linting and analyzing Python code, so you might be wondering why Refurb exists (skepticism is good!). As mentioned above, Refurb checks for code which can be made more elegant, something that no other linters (that I have found) specialize in. Here is a list of similar linters and analyzers, and how they differ from Refurb:
Black: is more focused on the formatting and styling of the code (line length, trailing comas, indentation, and so on). It does a really good job of making other projects using Black look more or less the same. It doesn't do more complex things such as type checking or code smell/anti-pattern detection.
flake8: flake8 is also a linter, is very extensible, and performs a lot of semantic analysis-related checks as well, such as "unused variable", "break outside of a loop", and so on. It also checks PEP8 conformance. Refurb won't try and replace flake8, because chances are you are already using flake8 anyways.
Pylint has a lot of checks which cover a lot of ground, but in general, are focused on bad or buggy code, things which you probably didn't mean to do. Refurb assumes that you know what you are doing, and will try to cleanup what is already there the best it can.
Mypy, Pyright, Pyre, and Pytype are all type checkers, and basically just enforce types, ensures arguments match, functions are called in a type safe manner, and so on. They do much more then that, but that is the general idea. Refurb actually is built on top of Mypy, and uses its AST parser so that it gets good type information.
pyupgrade: Pyupgrade has a lot of good checks for upgrading your older Python code to the newer syntax, which is really useful. Where Refurb differs is that Pyupgrade is more focused on upgrading your code to the newer version, whereas Refurb is more focused on cleaning up and simplifying what is already there.
In conclusion, Refurb doesn't want you to throw out your old tools, since they cover different areas of your code, and all serve a different purpose. Refurb is meant to be used in conjunction with the above tools.
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