import functools

import types

from collections.abc import Callable

from typing import TypeVar

# from jaraco.functools 3.3

def method_cache(method, cache_wrapper=None):

"""

Wrap lru_cache to support storing the cache data in the object instances.

Abstracts the common paradigm where the method explicitly saves an

underscore-prefixed protected property on first call and returns that

subsequently.

>>> class MyClass:

... calls = 0

...

... @method_cache

... def method(self, value):

... self.calls += 1

... return value

>>> a = MyClass()

>>> a.method(3)

3

>>> for x in range(75):

... res = a.method(x)

>>> a.calls

75

Note that the apparent behavior will be exactly like that of lru_cache

except that the cache is stored on each instance, so values in one

instance will not flush values from another, and when an instance is

deleted, so are the cached values for that instance.

>>> b = MyClass()

>>> for x in range(35):

... res = b.method(x)

>>> b.calls

35

>>> a.method(0)

0

>>> a.calls

75

Note that if method had been decorated with ``functools.lru_cache()``,

a.calls would have been 76 (due to the cached value of 0 having been

flushed by the 'b' instance).

Clear the cache with ``.cache_clear()``

>>> a.method.cache_clear()

Same for a method that hasn't yet been called.

>>> c = MyClass()

>>> c.method.cache_clear()

Another cache wrapper may be supplied:

>>> cache = functools.lru_cache(maxsize=2)

>>> MyClass.method2 = method_cache(lambda self: 3, cache_wrapper=cache)

>>> a = MyClass()

>>> a.method2()

3

Caution - do not subsequently wrap the method with another decorator, such

as ``@property``, which changes the semantics of the function.

See also

http://code.activestate.com/recipes/577452-a-memoize-decorator-for-instance-methods/

for another implementation and additional justification.

"""

cache_wrapper = cache_wrapper or functools.lru_cache()

def wrapper(self, *args, **kwargs):

# it's the first call, replace the method with a cached, bound method

bound_method = types.MethodType(method, self)

cached_method = cache_wrapper(bound_method)

setattr(self, method.__name__, cached_method)

return cached_method(*args, **kwargs)

# Support cache clear even before cache has been created.

wrapper.cache_clear = lambda: None

return wrapper

# From jaraco.functools 3.3

def pass_none(func):

"""

Wrap func so it's not called if its first param is None

>>> print_text = pass_none(print)

>>> print_text('text')

text

>>> print_text(None)

"""

@functools.wraps(func)

def wrapper(param, *args, **kwargs):

if param is not None:

return func(param, *args, **kwargs)

return wrapper

# From jaraco.functools 4.4

def noop(*args, **kwargs):

"""

A no-operation function that does nothing.

>>> noop(1, 2, three=3)

"""

_T = TypeVar('_T')

# From jaraco.functools 4.4

def passthrough(func: Callable[..., object]) -> Callable[[_T], _T]:

"""

Wrap the function to always return the first parameter.

>>> passthrough(print)('3')

3

'3'

"""

@functools.wraps(func)

def wrapper(first: _T, *args, **kwargs) -> _T:

func(first, *args, **kwargs)

return first

return wrapper # type: ignore[return-value]