python基础语法复习二

列表

li = [1,2,3,'456',[1,2,3],{1:'one',2: 'two'}]
print(type(li))

#元素访问 倒过来数 -1 倒数第一个 负数索引
print(li[-1])
print(li[-2])
# 查找元素位置
print(li.index('456'))
# 添加元素
l_a =[1,2,3]
l_a.append(4)
l_b =[6,7,8]
l_a.extend(l_b)# 加一个数组
# 判断为空
if not l_a:
    pass
if len(l_a) == 0:
    pass
#输出
for i in li:
    print(i)
for i in range(len(li)):
    print(li[i])

字典：

dict ={1:1,'one':'A','3245':'two'}
for key in dict:
    print(dict[key])
for key ,value in dict.items():
    print(key,value)

# set 判断元素是否存在
a_set =set([1,2,3,4,3,2,1])
b_set=set([3,5,6])
print(3 in a_set)
# 并集/交集/差集
#并集
print(a_set | b_set)
print(a_set.union(b_set))
#交集
print(a_set & b_set)
print(a_set.intersection(b_set))
#差集
print(a_set - b_set)
print(a_set.difference(b_set))
#
a_set.add(70)
a_set.update([4,5,6,7])
a_set.remove(7)

a=[1,2,3,4,5,6,7]
print(a[1:4])