使用set
l1 = ['b','c','d','b','c','a','a']
l2 = list(set(l1))
print (l2) # ['a', 'c', 'b', 'd']
# 或者
l2 = {}.fromkeys(l1).keys()
print (l2) # ['a', 'c', 'b', 'd']
这两种都有个缺点，去除重复元素后排序变了：
list的sort()保持顺序
l1 = ['b','c','d','b','c','a','a']
l2 = list(set(l1))
l2.sort(key=l1.index)
print (l2) # ['b','c','d','a']
# 或者
l1 = ['b','c','d','b','c','a','a']
l2 = sorted(set(l1),key=l1.index)
print (l2) # ['b','c','d','a']
遍历
l1 = ['b','c','d','b','c','a','a']
l2 = []
for i in l1:
if not i in l2:
l2.append(i)
print (l2) # ['b','c','d','a']
# 或者
l1 = ['b','c','d','b','c','a','a']
l2 = []
[l2.append(i) for i in l1 if not i in l2]
print (l2) # ['b','c','d','a']
