Python 强大的模式匹配工具—Pampy

 

 

https://pypi.org/project/pampy/

 

 

santinic/pampy: Pampy: The Pattern Matching for Python you always dreamed of. (github.com)

 

All the things you can match

As Pattern you can use any Python type, any class, or any Python value.

The operator _ and built-in types like int or str, extract variables that are passed to functions.

Types and Classes are matched via instanceof(value, pattern).

Iterable Patterns match recursively through all their elements. The same goes for dictionaries.

Pattern Example	What it means	Matched Example	Arguments Passed to function	NOT Matched Example
"hello"	only the string "hello" matches	"hello"	nothing	any other value
None	only None	None	nothing	any other value
int	Any integer	42	42	any other value
float	Any float number	2.35	2.35	any other value
str	Any string	"hello"	"hello"	any other value
tuple	Any tuple	(1, 2)	(1, 2)	any other value
list	Any list	[1, 2]	[1, 2]	any other value
MyClass	Any instance of MyClass. And any object that extends MyClass.	MyClass()	that instance	any other object
_	Any object (even None)		that value
ANY	The same as _		that value
(int, int)	A tuple made of any two integers	(1, 2)	1 and 2	(True, False)
[1, 2, _]	A list that starts with 1, 2 and ends with any value	[1, 2, 3]	3	[1, 2, 3, 4]
[1, 2, TAIL]	A list that start with 1, 2 and ends with any sequence	[1, 2, 3, 4]	[3, 4]	[1, 7, 7, 7]
{'type':'dog', age: _ }	Any dict with type: "dog" and with an age	{"type":"dog", "age": 3}	3	{"type":"cat", "age":2}
{'type':'dog', age: int }	Any dict with type: "dog" and with an int age	{"type":"dog", "age": 3}	3	{"type":"dog", "age":2.3}
re.compile('(\w+)-(\w+)-cat$')	Any string that matches that regular expression expr	"my-fuffy-cat"	"my" and "puffy"	"fuffy-dog"
Pet(name=_, age=7)	Any Pet dataclass with age == 7	Pet('rover', 7)	['rover']	Pet('rover', 8)
Any	The same as _		that value
Union[int, float, None]	Any integer or float number or None	2.35	2.35	any other value
Optional[int]	The same as Union[int, None]	2	2	any other value
Type[MyClass]	Any subclass of MyClass. And any class that extends MyClass.	MyClass	that class	any other object
Callable[[int], float]	Any callable with exactly that signature	def a(q:int) -> float: ...	that function	def a(q) -> float: ...
Tuple[MyClass, int, float]	The same as (MyClass, int, float)
Mapping[str, int] Any subtype of Mapping acceptable too	any mapping or subtype of mapping with string keys and integer values	{'a': 2, 'b': 3}	that dict	{'a': 'b', 'b': 'c'}
Iterable[int] Any subtype of Iterable acceptable too	any iterable or subtype of iterable with integer values	range(10) and [1, 2, 3]	that iterable	['a', 'b', 'v']

Using default

By default match() is strict. If no pattern matches, it raises a MatchError.

You can instead provide a fallback value using default to be used when nothing matches.

>>> match([1, 2], [1, 2, 3], "whatever")
MatchError: '_' not provided. This case is not handled: [1, 2]

>>> match([1, 2], [1, 2, 3], "whatever", default=False)
False

Using Regular Expressions

Pampy supports Python's Regex. You can pass a compiled regex as pattern, and Pampy is going to run pattern.search(), and then pass to the action function the result of .groups().

def what_is(pet):
    return match(pet,
        re.compile('(\w+)-(\w+)-cat$'),     lambda name, my: 'cat '+name,
        re.compile('(\w+)-(\w+)-dog$'),     lambda name, my: 'dog '+name,
        _,                                  "something else"
    )

what_is('fuffy-my-dog')     # => 'dog fuffy'
what_is('puffy-her-dog')    # => 'dog puffy'
what_is('carla-your-cat')   # => 'cat carla'
what_is('roger-my-hamster') # => 'something else'