flake8 plugin which checks for code that can be simplified
Project description
flake8-simplify
A flake8 plugin that helps you simplify your code.
Installation
Install with pip
:
pip install flake8-simplify
Python 3.6 to 3.8 are supported.
Usage
Just call flake8 .
in your package or flake your.py
:
$ flake8 .
./foo/__init__.py:690:12: SIM101 Multiple isinstance-calls which can be merged into a single call for variable 'other'
Rules
Python-specific rules:
SIM101
: Multiple isinstance-calls which can be merged into a single call by using a tuple as a second argument (example)SIM104
: Use 'yield from iterable' (introduced in Python 3.3, see PEP 380) (example)
SIM105
: Use 'contextlib.suppress(...)' instead of try-except-pass (example)SIM107
: Don't usereturn
in try/except and finally (example)SIM108
: Use the ternary operator if it's reasonable (example)SIM109
: Use a tuple to compare a value against multiple values (example)SIM110
: Use any(...) (example)SIM111
: Use all(...) (example)SIM113
: Use enumerate instead of manually incrementing a counter (example)SIM114
: Combine conditions via a logical or to prevent duplicating code (example)SIM115
: Use context handler for opening files (example)SIM116
: Use a dictionary instead of many if/else equality checks (example)SIM117
: Merge with-statements that use the same scope (example)SIM119
:Moved to flake8-scream due to issue 63
SIM120
: Use 'class FooBar:' instead of 'class FooBar(object):' (example)
SIM121
: Reserved for SIM908 once it's stableSIM124
: Reserved for SIM904 once it's stableSIM125
: Reserved for SIM905 once it's stableSIM126
: Reserved for SIM906 once it's stableSIM127
: Reserved for SIM907 once it's stable
Simplifying Comparations:
SIM201
: Use 'a != b' instead of 'not a == b' (example)SIM202
: Use 'a == b' instead of 'not a != b' (example)SIM203
: Use 'a not in b' instead of 'not (a in b)' (example)SIM204
:Moved to flake8-scream due to issue 116
SIM205
:Moved to flake8-scream due to issue 116
SIM206
:Moved to flake8-scream due to issue 116
SIM207
:Moved to flake8-scream due to issue 116
SIM208
: Use 'a' instead of 'not (not a)' (example)SIM210
: Use 'bool(a)' instead of 'True if a else False' (example)SIM211
: Use 'not a' instead of 'False if a else True' (example)SIM212
: Use 'a if a else b' instead of 'b if not a else a' (example)SIM220
: Use 'False' instead of 'a and not a' (example)SIM221
: Use 'True' instead of 'a or not a' (example)SIM222
: Use 'True' instead of '... or True' (example)SIM223
: Use 'False' instead of '... and False' (example)SIM224
: Reserved for SIM901 once it's stableSIM300
: Use 'age == 42' instead of '42 == age' (example)
Simplifying usage of dictionaries:
SIM401
: Use 'a_dict.get(key, "default_value")' instead of an if-block (example)SIM118
: Use 'key in dict' instead of 'key in dict.keys()' (example)
General Code Style:
SIM102
: Use a single if-statement instead of nested if-statements (example)SIM103
: Return the boolean condition directly (example)SIM106
: Handle error-cases first (example). This rule was removed due to too many false-positives.SIM112
: Use CAPITAL environment variables (example)SIM122
/ SIM902:Moved to flake8-scream due to issue 125
SIM123
: Reserved for SIM903 once it's stableSIM124
: Reserved for SIM909 once it's stable
Experimental rules:
Getting rules right for every possible case is hard. I don't want to disturb
peoples workflows. For this reason, flake8-simplify introduces new rules with
the SIM9
prefix. Every new rule will start with SIM9 and stay there for at
least 6 months. In this time people can give feedback. Once the rule is stable,
the code will change to another number.
Current experimental rules:
SIM901
: Use comparisons directly instead of wrapping them in abool(...)
call (example)SIM903
: Use keyword-argument instead of magic number (example)SIM904
: Assign values to dictionary directly at initialization (example)SIM905
: Split string directly if only constants are used (example)SIM906
: Merge nested os.path.join calls (example)SIM907
: Use Optional[Type] instead of Union[Type, None] (example)SIM908
: Use dict.get(key) (example)
Disabling Rules
You might have good reasons to
ignore some flake8 rules.
To do that, use the standard Flake8 configuration. For example, within the setup.cfg
file:
[flake8]
ignore = SIM106, SIM113, SIM119, SIM9
Examples
SIM101
# Bad
isinstance(a, int) or isinstance(a, float)
# Good
isinstance(a, (int, float))
SIM102
# Bad
if a:
if b:
c
# Good
if a and b:
c
SIM105
# Bad
try:
foo()
except ValueError:
pass
# Good
from contextlib import suppress
with suppress(ValueError):
foo()
Please note that contextlib.suppress
is roughly 3x slower than try/except
(source).
SIM107
# Bad: This example returns 3!
def foo():
try:
1 / 0
return "1"
except:
return "2"
finally:
return "3"
# Good
def foo():
return_value = None
try:
1 / 0
return_value = "1"
except:
return_value = "2"
finally:
return_value = "3" # you might also want to check if "except" happened
return return_value
SIM108
# Bad
if a:
b = c
else:
b = d
# Good
b = c if a else d
SIM109
# Bad
if a == b or a == c:
d
# Good
if a in (b, c):
d
SIM110
# Bad
for x in iterable:
if check(x):
return True
return False
# Good
return any(check(x) for x in iterable)
SIM111
# Bad
for x in iterable:
if check(x):
return False
return True
# Good
return all(not check(x) for x in iterable)
SIM112
# Bad
os.environ["foo"]
os.environ.get("bar")
# Good
os.environ["FOO"]
os.environ.get("BAR")
SIM113
Using enumerate
in simple cases like the loops below is a tiny bit easier to read as the reader does not have to figure out where / when the loop variable is incremented (or if it is incremented in multiple places).
# Bad
idx = 0
for el in iterable:
...
idx += 1
# Good
for idx, el in enumerate(iterable):
...
SIM114
# Bad
if a:
b
elif c:
b
# Good
if a or c:
b
SIM115
# Bad
f = open(...)
... # (do something with f)
f.close()
# Good
with open(...) as f:
... # (do something with f)
SIM116
# Bad
if a == "foo":
return "bar"
elif a == "bar":
return "baz"
elif a == "boo":
return "ooh"
else:
return 42
# Good
mapping = {"foo": "bar", "bar": "baz", "boo": "ooh"}
return mapping.get(a, 42)
SIM117
# Bad
with A() as a:
with B() as b:
print("hello")
# Good
with A() as a, B() as b:
print("hello")
Thank you for pointing this one out, Aaron Gokaslan!
SIM118
# Bad
key in a_dict.keys()
# Good
key in a_dict
Thank you for pointing this one out, Aaron Gokaslan!
SIM120
# Bad
class FooBar(object):
...
# Good
class FooBar:
...
Both notations are equivalent in Python 3, but the second one is shorter.
SIM201
# Bad
not a == b
# Good
a != b
SIM202
# Bad
not a != b
# Good
a == b
SIM203
# Bad
not a in b
# Good
a not in b
SIM208
# Bad
not (not a)
# Good
a
SIM210
# Bad
True if a else False
# Good
bool(a)
SIM211
# Bad
False if a else True
# Good
not a
SIM212
# Bad
b if not a else a
# Good
a if a else b
SIM220
# Bad
a and not a
# Good
False
SIM221
# Bad
a or not a
# Good
True
SIM222
# Bad
... or True
# Good
True
SIM223
# Bad
... and False
# Good
False
SIM300
# Bad; This is called a "Yoda-Condition"
42 == age
# Good
age == 42
SIM401
# Bad
if key in a_dict:
value = a_dict[key]
else:
value = "default_value"
# Good
thing = a_dict.get(key, "default_value")
SIM901
This rule will be renamed to SIM224
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 23rd of January and will end on 23rd of August 2022.
# Bad
bool(a == b)
# Good
a == b
SIM903
This rule will be renamed to SIM123
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 12th of February and will end on 12th of September 2022.
# Bad
foo(42, 1.234)
# Good
foo(the_answer=42, flux_compensation=1.234)
SIM904
This rule will be renamed to SIM224
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 12th of February and will end on 12th of September 2022.
# Bad
a = {}
a["b"] = "c"
# Good
a = {"b": "c"}
SIM905
This rule will be renamed to SIM225
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 13th of February and will end on 13th of September 2022.
# Bad
domains = "de com net org".split()
# Good
domains = ["de", "com", "net", "org"]
SIM906
This rule will be renamed to SIM126
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 20th of February and will end on 20th of September 2022.
# Bad
os.path.join(a, os.path.join(b, c))
# Good
os.path.join(a, b, c)
SIM907
This rule will be renamed to SIM127
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 28th of March and will end on 28th of September 2022.
# Bad
def foo(a: Union[int, None]) -> Union[int, None]:
return a
# Good
def foo(a: Optional[int]) -> Optional[int]:
return a
SIM908
This rule will be renamed to SIM121
after its 6-month trial period is over.
Please report any issues you encounter with this rule!
The trial period starts on 28th of March and will end on 28th of September 2022.
# Bad
name = "some_default"
if "some_key" in some_dict:
name = some_dict["some_key"]
# Good
name = some_dict.get("some_key", "some_default")
SIM909
Thank you Ryan Delaney for the idea!
The trial period starts on 28th of March and will end on 28th of September 2022.
# Bad
foo = foo
# Good: Nothing. Reflexive assignments have no purpose.
or
# Bad
foo = foo = 42
# Good
foo = 42
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