我的代码类似于:
long ms = 86400000;
long s = ms % 60;
long m = (ms / 60) % 60;
long h = (ms / (60 * 60)) % 24;
String timeFind = String.format("%d:%02d:%02d", h, m, s);
我可以成功运行过滤测试,例如:
import operator
class Comparator:
def __init__(self,fieldName,compareToValue,my_operator):
self.op = my_operator
self.field = fieldName
self.comparedTo = compareToValue
def __call__(self,row):
my_row_val = getattr(row,self.field)
return self.op(my_row_val,self.comparedTo)
class Row:
class RowItem:
def __init__(self,name):
self.name = name
def __eq__(self,other):
return Comparator(self.name,other,operator.eq)
val1 = RowItem("val1")
val2 = RowItem("val2")
val3 = RowItem("val3")
val4 = RowItem("val4")
def __init__(self, val1, val2, val3, val4):
self.val1 = val1
self.val2 = val2
self.val3 = val3
self.val4 = val4
def __str__(self):
return str([self.val1,self.val2,self.val3,self.val4])
def __repr__(self):
return str(self)
class MyTable:
def __init__(self,rows):
self.rows = rows
def filter(self,condition):
for row in self.rows:
if condition(row):
yield row
rows = [Row(1,2,3,"hello"),Row(1,2,7,"cat"),Row(1,2,3,"hi"),Row(7,7,7,"foo")]
mytable = MyTable(rows)
但是当我尝试使用print list(mytable.filter(Row.val3 == 7))
# prints [[1, 2, 7, 'cat'], [7, 7, 7, 'foo']]
print list(mytable.filter(Row.val2 == 2))
# prints [[1, 2, 3, 'hello'], [1, 2, 7, 'cat'], [1, 2, 3, 'hi']]
时,它无法正常工作:
and
我如何才能正常工作?
答案 0 :(得分:3)
您无法挂钩and
和or
逻辑运算符,因为它们short-circuit;首先评估左手表达式,如果该表达式的结果确定结果,则永远不会评估右手表达式。该操作返回最后一个表达式的值。
在你的情况下,(Row.val3 == 7) and (Row.val2 == 2)
表达式首先评估(Row.val3 == 7)
,因为它返回一个没有任何特定钩子的实例,否则它是considered a true value,所以右边的结果然后返回-hand表达式。
你可以在这里使用&
and |
(bitwise AND and OR) operators,这些委托给object.__and__
和object.__or__
个钩子。这就像SQLAlchemy那样的ORM库。
相应的operator
函数为operator.and_
和operator.or_
。