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("")`
Before installing, it is recommended that you setup a virtual environment.
$ pip3 install refurb
$ refurb file.py folder/
Note: Refurb only supports Python 3.10. It can check Python 3.6 code and up, but Refurb itself must be ran through Python 3.10.
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
```
Use --ignore 123
to ignore error 123. The error code can be in the form FURB123
or 123
.
This flag can be repeated.
The
FURB
prefix indicates that this is a built-in error. TheFURB
prefix 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() # noqa
Here, noqa: FURB123
specifically ignores the FURB123 error for that line, and noqa
ignores
all errors on that line.
Certain 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.
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_all
andenable_all
are mutually exclusive, both on the command line and in the config file. You will get an error if you try to specify both.
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
.
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 = true
Now 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.
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: refurb
Replacing 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:
$ pip3 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
fzf
fuzzy-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.here
is a directory, all checks in that directory will be loaded. If it is a file, only that file will be loaded.
To setup locally, run:
$ git clone https://github.com/dosisod/refurb
$ cd refurb
$ make install
$ make install-local
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-e2e
to run them.
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, and Pyre 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.