Python 检查条件的更简单方法?
我是python新手,需要简化这个检查器。我怎样才能改变:Python 检查条件的更简单方法?,python,multiple-conditions,Python,Multiple Conditions,我是python新手,需要简化这个检查器。我怎样才能改变: ... if c == '>' and ( prevTime > currentTime ): c2 = True elif c == '>=' and ( prevTime >= currentTime ): c2 = True ... 例如: if prevTime | condition | currentTime: doSomething() >>> e
...
if c == '>' and ( prevTime > currentTime ):
c2 = True
elif c == '>=' and ( prevTime >= currentTime ):
c2 = True
...
例如:
if prevTime | condition | currentTime:
doSomething()
>>> eval('datetime.now() %s datetime.utcfromtimestamp(41)' % '>')
True
我尝试过使用求值或编译,但在创建字符串的过程中,datetime对象与字符串之间存在转换(stron datetime对象)。例如:
>>> 'result = %s %s %s' % (datetime.now(), '>', datetime.utcfromtimestamp(41))
'result = 2011-04-07 14:13:34.819317 > 1970-01-01 00:00:41'
这是无法比较的
有人能帮我吗?以下工作示例:
def checkEvent( prevEvent, currentEvent, prevTime, currentTime ):
def checkCondition( condition ):
#condition format
#tuple ( (oldEvent, newEvent), time, ip)
# eg: (('co', 'co'), '>=', '!=')
c1 = c2 = False
#check Event
if prevEvent == condition[0][0] and currentEvent == condition[0][1]:
c1 = True
else:
return False
#check time
if condition[1]:
c = condition[1]
if c == '>' and ( prevTime > currentTime ):
c2 = True
elif c == '>=' and ( prevTime >= currentTime ):
c2 = True
elif c == '<' and ( prevTime < currentTime ):
c2 = True
elif c == '<=' and ( prevTime <= currentTime ):
c2 = True
elif c == '==' and ( prevTime == currentTime ):
c2 = True
else:
c2 = True
return c1 and c2
def add():
print 'add'
def changeState():
print 'changeState'
def finish():
print 'finish'
def update():
print 'update'
conditions = (\
( ( ( 're', 'co' ), None ), ( add, changeState ) ),
( ( ( 'ex', 'co' ), None ), ( add, changeState ) ),
( ( ( 'co', 'co' ), '<' ), ( add, changeState ) ),
( ( ( 'co', 'co' ), '>=' ), ( add, changeState, finish ) ),
( ( ( 'co', 'co' ), '>=' ), ( update, ) ),
( ( ( 'co', 're' ), '>=' ), ( changeState, finish ) ),
( ( ( 'co', 'ex' ), '>=' ), ( changeState, finish ) )
)
for condition in conditions:
if checkCondition( condition[0] ):
for cmd in condition[1]:
cmd()
from datetime import datetime
checkEvent( 'co', 'co', datetime.utcfromtimestamp(41), datetime.now() )
checkEvent( 'ex', 'co', datetime.utcfromtimestamp(41), datetime.now() )
checkEvent( 'co', 'co', datetime.utcfromtimestamp(41), datetime.utcfromtimestamp(40) )
def checkEvent(prevEvent、currentEvent、prevTime、currentTime):
def检查条件(条件):
#条件格式
#元组((oldEvent,newEvent),时间,ip)
#例如:(('co','co'),'>=','!=')
c1=c2=False
#检查事件
如果prevEvent==条件[0][0]和currentEvent==条件[0][1]:
c1=真
其他:
返回错误
#检查时间
如果条件[1]:
c=条件[1]
如果c=='>'和(prevTime>currentTime):
c2=真
elif c=='>='和(prevTime>=currentTime):
c2=真
elif c=='='),(changeState,finish)),
((('co','ex'),'>='),(变更状态,完成))
)
对于条件中的条件:
如果检查条件(条件[0]):
对于条件[1]中的cmd:
cmd()
从日期时间导入日期时间
checkEvent('co','co',datetime.utcfromtimestamp(41),datetime.now())
checkEvent('ex','co',datetime.utcfromtimestamp(41),datetime.now())
checkEvent('co','co',datetime.utcfromtimestamp(41),datetime.utcfromtimestamp(40))
人们会这样做:
result= { '=': lambda a, b: a == b,
'>': lambda a, b: a > b,
'>=': lambda a, b: a >= b,
etc.
}[condition]( prevTime, currentTime )
import operator
compares = {
'>': operator.gt,
'>=': operator.ge,
'<': operator.lt,
'<=': operator.le,
'==': operator.eq
}
def check(c, prev, current):
func = compares[c]
return func(prev, current)
print check('>', 5, 3) # prints: True
print check('>=', 5, 5) # prints: True
print check('<', 3, 5) # prints: True
print check('<=', 3, 3) # prints: True
print check('==', 7, 7) # prints: True
您可以尝试制作操作符的映射,如下所示:
result= { '=': lambda a, b: a == b,
'>': lambda a, b: a > b,
'>=': lambda a, b: a >= b,
etc.
}[condition]( prevTime, currentTime )
import operator
compares = {
'>': operator.gt,
'>=': operator.ge,
'<': operator.lt,
'<=': operator.le,
'==': operator.eq
}
def check(c, prev, current):
func = compares[c]
return func(prev, current)
print check('>', 5, 3) # prints: True
print check('>=', 5, 5) # prints: True
print check('<', 3, 5) # prints: True
print check('<=', 3, 3) # prints: True
print check('==', 7, 7) # prints: True
导入操作符
比较={
“>”:operator.gt,
“>=”:operator.ge,
“=”,5,5)#打印:对
打印检查(“您是否正在寻找以下内容:
if prevTime | condition | currentTime:
doSomething()
>>> eval('datetime.now() %s datetime.utcfromtimestamp(41)' % '>')
True
你的评估失败是因为你在评估之外做了太多的计算
当然,eval策略本身很难看;您应该使用其他答案中的一个;)如果函数没有返回,您只需要设置c1=True
,因此在函数结束时它保证为True。将其考虑在内
此功能的输出将相同:
def checkEvent( prevEvent, currentEvent, prevTime, currentTime ):
def checkCondition( condition ):
#condition format
#tuple ( (oldEvent, newEvent), time, ip)
# eg: (('co', 'co'), '>=', '!=')
#check Event
if not (prevEvent == condition[0][0] and currentEvent == condition[0][1]):
return False
#check time
c = condition[1]
if not condition[1]:
return True
if c == '>' and ( prevTime > currentTime ):
return True
elif c == '>=' and ( prevTime >= currentTime ):
return True
elif c == '<' and ( prevTime < currentTime ):
return True
elif c == '<=' and ( prevTime <= currentTime ):
return True
elif c == '==' and ( prevTime == currentTime ):
return True
return False
def checkEvent(prevEvent、currentEvent、prevTime、currentTime):
def检查条件(条件):
#条件格式
#元组((oldEvent,newEvent),时间,ip)
#例如:(('co','co'),'>=','!=')
#检查事件
如果不是(prevEvent==条件[0][0]和currentEvent==条件[0][1]):
返回错误
#检查时间
c=条件[1]
如果不是条件[1]:
返回真值
如果c=='>'和(prevTime>currentTime):
返回真值
elif c=='>='和(prevTime>=currentTime):
返回真值
elif c=='+1:但是,lambda!你没有收到备忘录吗?(我也没有收到;别担心。)事实上,我已经读到BDFL不喜欢lambda的消息——它可能会被滥用。f=lambda x:return“太懒了,无法编写def”
非常令人反感。我没有考虑使用lambdas。它看起来非常紧凑。真正的checker要大得多,不仅比较datetime,还比较IP、MAC等。我认为这是最好的解决方案。谢谢。@max:虽然它可能被滥用,但它允许您在将字符串映射到函数时有很大的灵活性。只要function非常简单。如果函数变得复杂,就没有理由只为了保留lambda而编写扭曲的代码。有时,复杂函数需要一个一流的def
。此外,import操作符as op
大大缩短了这一过程,并使lambda批评者感到高兴。确切地说,使用操作符或lambda的解决方案是可行的ce:)你说得对!我以前提到过,这个例子是原例子的缩短版。