我想取列表x和y的差值:
>>> x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> y = [1, 3, 5, 7, 9]
>>> x - y
# should return [0, 2, 4, 6, 8]
我想取列表x和y的差值:
>>> x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> y = [1, 3, 5, 7, 9]
>>> x - y
# should return [0, 2, 4, 6, 8]
当前回答
如果列表允许重复元素,你可以使用Counter from collections:
from collections import Counter
result = list((Counter(x)-Counter(y)).elements())
如果你需要保留x中元素的顺序:
result = [ v for c in [Counter(y)] for v in x if not c[v] or c.subtract([v]) ]
其他回答
这个例子减去了两个列表:
# List of pairs of points
list = []
list.append([(602, 336), (624, 365)])
list.append([(635, 336), (654, 365)])
list.append([(642, 342), (648, 358)])
list.append([(644, 344), (646, 356)])
list.append([(653, 337), (671, 365)])
list.append([(728, 13), (739, 32)])
list.append([(756, 59), (767, 79)])
itens_to_remove = []
itens_to_remove.append([(642, 342), (648, 358)])
itens_to_remove.append([(644, 344), (646, 356)])
print("Initial List Size: ", len(list))
for a in itens_to_remove:
for b in list:
if a == b :
list.remove(b)
print("Final List Size: ", len(list))
from collections import Counter
y = Counter(y)
x = Counter(x)
print(list(x-y))
使用一个列表推导式来计算差值,同时保持x的原始顺序:
[item for item in x if item not in y]
如果你不需要列表属性(例如,排序),使用一个集差异,正如其他答案所建议的:
list(set(x) - set(y))
为了允许x - y中缀语法,在从list继承的类上重写__sub__:
class MyList(list):
def __init__(self, *args):
super(MyList, self).__init__(args)
def __sub__(self, other):
return self.__class__(*[item for item in self if item not in other])
用法:
x = MyList(1, 2, 3, 4)
y = MyList(2, 5, 2)
z = x - y
def listsubtraction(parent,child):
answer=[]
for element in parent:
if element not in child:
answer.append(element)
return answer
我认为这应该可行。我是初学者,所以请原谅我的错误
在set中查找值比在list中查找值更快:
[item for item in x if item not in set(y)]
我相信这将会比:
[item for item in x if item not in y]
两者都保持了列表的顺序。