In some applications, it's advantageous to be able to define a fixed length list.
The class provides all features as python internal type: list
The main focus of fixed length list is only keep certain number of items. "overflow" items will be discarded.
Python, 51 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | class FixedlenList(list):
'''
subclass from list, providing all features list has
the list size is fixed. overflow items will be discarded
'''
def __init__(self,l=0):
super(FixedlenList,self).__init__()
self.__length__=l #fixed length
def pop(self,index=-1):
super(FixedlenList, self).pop(index)
def remove(self,item):
self.__delitem__(item)
def __delitem__(self,item):
super(FixedlenList, self).__delitem__(item)
#self.__length__-=1
def append(self,item):
if len(self) >= self.__length__:
super(FixedlenList, self).pop(0)
super(FixedlenList, self).append(item)
def extend(self,aList):
super(FixedlenList, self).extend(aList)
self.__delslice__(0,len(self)-self.__length__)
def insert(self):
pass
##################
# test cases
##################
def test1():
l=FixedlenList(5)
l.append(1)
l.append(2)
l.append(3)
l.append(4)
l.append(5)
l.append(6)
print repr(l)=='[2, 3, 4, 5, 6]'
def test2():
l=FixedlenList(2)
l.extend([11,12,13])
print repr(l)=='[12, 13]'
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