transitions在运行时向模型 ( Matter) 实例添加触发器。在实际执行初始化代码之前，IDE 无法预测这一点。恕我直言，这是工作方式的最大缺点transitions（但恕我直言，在处理动态状态机或在运行时创建/接收的状态机时，这也是它的优势，但这是另一回事）
如果您使用带有代码完成功能的交互式 shell (ipython)，您将看到evaporate（基于对__dir__模型的调用）将被建议：
from transitions import Machine
class Model:
pass
model = Model()
>>> model.e # TAB -> nothing
# model will be decorated during machine initialization
machine = Machine(model, states=['A', 'B'],
transitions=[['evaporate', 'A', 'B']], initial='A')
>>> model.e # TAB -> completion!
但我认为这不是您计划编码的方式。那么我们怎样才能给内省提示呢？
最简单的解决方案：为您的模型使用文档字符串来宣布触发器。
from transitions import Machine
class Model:
"""My dynamically extended Model
Attributes:
evaporate(callable): dynamically added method
"""
model = Model()
# [1]
machine = Machine(model, states=['A', 'B'],
transitions=[['evaporate', 'A', 'B']], initial='A')
model.eva # code completion! will also suggest 'evaporate' before it was added at [1]
这里的问题是 IDE 将依赖于文档字符串是正确的。因此，当 docstring 方法（被屏蔽为属性）被调用evaparate时，它总是会建议即使您稍后添加evaporate.
使用pyi文件和PEP484（PyCharm 解决方法）
不幸的是，正如您正确指出的那样，PyCharm 没有考虑文档字符串中的属性来完成代码（有关更多详细信息，请参阅此讨论）。我们需要使用另一种方法。我们可以创建所谓的pyi文件来为 PyCharm 提供提示。这些文件的名称与它们的.py对应文件相同，但仅用于 IDE 和其他工具，不得导入（参见这篇文章）。让我们创建一个名为sandbox.pyi
# sandbox.pyi
class Model:
evaporate = None # type: callable
现在让我们创建实际的代码文件sandbox.py（我没有将我的游乐场文件命名为“test”，因为这总是让 pytest 感到吃惊......）
# sandbox.py
from transitions import Machine
class Model:
pass
## Having the type hints right here would enable code completion BUT
## would prevent transitions to decorate the model as it does not override
## already defined model attributes and methods.
# class Model:
# evaporate = None # type: callable
model = Model()
# machine initialization
model.ev # code completion
这样您就可以完成代码transitions并正确装饰模型。缺点是您要担心另一个文件可能会使您的项目混乱。
如果您想pyi自动生成文件，您可以查看stubgen或扩展Machine来为您生成模型的事件存根。
from transitions import Machine
class Model:
pass
class PyiMachine(Machine):
def generate_pyi(self, filename):
with open(f'{filename}.pyi', 'w') as f:
for model in self.models:
f.write(f'class {model.__class__.__name__}:\n')
for event in self.events:
f.write(f' def {event}(self, *args, **kwargs) -> bool: pass\n')
f.write('\n\n')
model = Model()
machine = PyiMachine(model, states=['A', 'B'],
transitions=[['evaporate', 'A', 'B']], initial='A')
machine.generate_pyi('sandbox')
# PyCharm can now correctly infer the type of success
success = model.evaporate()
model.to_A() # A dynamically added method which is now visible thanks to the pyi file
替代方案：从文档字符串生成机器配置
在转换的问题跟踪器中已经讨论了一个类似的问题（参见https://github.com/pytransitions/transitions/issues/383）。您还可以从模型的文档字符串生成机器配置：
import transitions
import inspect
import re
class DocMachine(transitions.Machine):
"""Parses states and transitions from model definitions"""
# checks for 'attribute:value' pairs (including [arrays]) in docstrings
re_pattern = re.compile(r"(\w+):\s*\[?([^\]\n]+)\]?")
def __init__(self, model, *args, **kwargs):
conf = {k: v for k, v in self.re_pattern.findall(model.__doc__, re.MULTILINE)}
if 'states' not in kwargs:
kwargs['states'] = [x.strip() for x in conf.get('states', []).split(',')]
if 'initial' not in kwargs and 'initial' in conf:
kwargs['initial'] = conf['initial'].strip()
super(DocMachine, self).__init__(model, *args, **kwargs)
for name, method in inspect.getmembers(model, predicate=inspect.ismethod):
doc = method.__doc__ if method.__doc__ else ""
conf = {k: v for k, v in self.re_pattern.findall(doc, re.MULTILINE)}
# if docstring contains "source:" we assume it is a trigger definition
if "source" not in conf:
continue
else:
conf['source'] = [s.strip() for s in conf['source'].split(', ')]
conf['source'] = conf['source'][0] if len(conf['source']) == 1 else conf['source']
if "dest" not in conf:
conf['dest'] = None
else:
conf['dest'] = conf['dest'].strip()
self.add_transition(trigger=name, **conf)
# override safeguard which usually prevents accidental overrides
def _checked_assignment(self, model, name, func):
setattr(model, name, func)
class Model:
"""A state machine model
states: [A, B]
initial: A
"""
def go(self):
"""processes information
source: A
dest: B
conditions: always_true
"""
def cycle(self):
"""an internal transition which will not exit the current state
source: *
"""
def always_true(self):
"""returns True... always"""
return True
def on_exit_B(self): # no docstring
raise RuntimeError("We left B. This should not happen!")
m = Model()
machine = DocMachine(m)
assert m.is_A()
m.go()
assert m.is_B()
m.cycle()
try:
m.go() # this will raise a MachineError since go is not defined for state B
assert False
except transitions.MachineError:
pass
这是一个非常简单的 docstring-to-machine-configration 解析器，它不会处理可能成为 docstring 一部分的所有可能性。它假定每个带有包含 ("source: ") 的文档字符串的方法都应该是一个触发器。然而，它也解决了文档问题。使用这样的机器将确保至少存在一些开发机器的文档。