Question

我基本上在下面的Start()方法中定义了一组参数。除了request.Continuation可以具有6或3的值以外，大多数参数都相同。我的想法是要列出一个将得到值6的符号列表（在self.continuation中），并说诸如“如果在self.continuation中，值为= 6，否则为3”。

我对python来说还很陌生，所以这可能还很遥远，但是我不确定这是否是lambda表达式的好用例。

class BarsRequestSample(CELEnvironment.CELSinkBase):
    def __init__(self):

        self.symbols = ['CLES12Z', 'HOE']
        self.continuation=['ClES12Z', 'CLES6M']

    def Start(self):    
        for symbol in self.symbols:
            request.Symbol = symbol
            request.RangeStart = 0
            request.RangeEnd = -60
            request.IntradayPeriod = 5
            request.Continuation = 6
            request.UpdatesEnabled = True
            request.EqualizeCloses = True
            request.SessionsFilter = 31

我知道我能做的事

def Start(self):

    for symbol in self.symbols:
        request.Symbol = symbol
        request.RangeStart = 0
        request.RangeEnd = -60
        request.IntradayPeriod = 5

        #potential attempt
        if symbol in self.continuation:
            request.Continuation = 6
        else:
            request.Continuation = 3

        request.UpdatesEnabled = True
        request.EqualizeCloses = True
        request.SessionsFilter = 31

我只是直觉，可能会有更简洁的方法来做同样的事情-感激任何想法！

Answer 1

我将符号列表设为一组。集包含是O（1）操作，而列表是O（n）。对于两个元素来说都没有关系，但这是一个很好的习惯。

self.continuation = {'ClES12Z', 'CLES6M'}

您可以使用conditional expression将分配压缩为一行：

request.Continuation = 6 if symbol in self.continuation else 3

Answer 2

对于lambda：

https://github.com/baruchel/continuation/blob/master/continuation/init.py

"""
A module for adding a call/cc feature to Python.
"""

__version__ = '0.1'

__internal_type_error__ = (
    "Argument of a continuation must be a continuable function."
    )

class _Continuation(Exception):
    def __init__(self, f, args, kwargs):
        self.func, self.args, self.kwargs = f, args, kwargs

class Continuation():
    def __init__(self, calling_id):
        self.calling_id = calling_id
    def __callback__(self, f):
        if isinstance(f, _Continuation):
            f.uid = id(self)
            raise f
        raise TypeError(__internal_type_error__)
    def __call__(self, f):
        return lambda *args, **kwargs: self.__callback__(f(*args, **kwargs))
    __lshift__ = __call__

def with_continuation(func):
    def _w(*args, **kwargs):
        return _Continuation(func, args, kwargs)
    _w.__with_continuation_signature__ = True
    return _w

class _with_CC():
    def __call__(self, f):
        try:
            _ = f.__with_continuation_signature__
        except AttributeError:
            raise TypeError(__internal_type_error__)
        return (
            lambda *args, **kwargs:
                _with_CC().__callback__(f(*args, **kwargs)))
    __rshift__ = __call__
    def __callback__(self, f):
        k = Continuation(id(self))
        i = id(k)
        while True:
            try:
                return (f.func)(k)(*f.args, **f.kwargs)
            except _Continuation as e:
                if i == e.uid: f = e
                else: raise e

with_CC = _with_CC()

应用条件If语句的最佳方法

2 个答案: