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<p>我试图实现contains,这样它就可以用于python对象中的任何一个属性。我能够成功地实现“==”和大多数其他比较运算符,但是“in”给我带来了问题:</p>
<pre><code>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)
def __contains__(self,other):
return Comparator(self.name,other,operator.contains)
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)
# the line below works fine!
print list(mytable.filter(Row.val3 == 7))
# this line below does not work
print list(mytable.filter("h" in Row.val4))
# TypeError: 'bool' object is not callable
# this line also does not work
print list(mytable.filter(Row.val4 in "hello world"))
# TypeError: 'in <string>' requires string as left operand, not instance
</code></pre>