python字典与集合常用操作

字典操作

• 创建空字典

d = {}

• 测试键k是否为字典成员

if k in d:
if d.has_key(k):

• 取键k对应的项

# be sure k exists in dict d
d[k]

# not sure k exists in dict d
d.get(k, defval)

• 删除键k对应的项

# be sure k exists in dict d
del d[k]
d.pop(k)

# not sure k exists in dict d
d.pop(k, defret)

• 遍历字典

for k in d.keys(): print(k)
for v in d.values(): print(v)
for k,v in d.items(): print(k, v)

集合操作

• 创建空集合

s = set()

• 用列表创建集合

s = set([3,4,6,8])
s = set('hello')

• 集合运算

s = a | b
s = a & b
s = a - b
s = a ^ b

• 添加元素

# insert single element
s.add(x)

# insert elements by list
s.update([3,2,4,9])

• 删除元素

# be sure x exists in set
s.remove(x)

# not sure x exists in set
s.discard(x)

• 检测x是否在集合中

if x in s:

• 遍历集合

for i in s: print(i)
for i in sorted(s): print(i)