Python 字典

Posted 2022-06-08 jkklearn

字典的定义

dic = "name":"zhangsan","age":7,"val":"math":60,"eng":80

值的输出

print dic["name"]   #zhangsan
print dic["val"]["math"]  #60

字典的遍历

dic = "name":"zhangsan","age":7,"val":"math":60,"eng":80

print "only key"
for key in dic.keys():
    print key

print "only val"
for val in dic.values():
    print val
print "both"
for key,val in dic.items():
    print key,val
输出的结果:

$ python test.py
only key
age
name
val
only val
7
zhangsan
‘math‘: 60, ‘eng‘: 80
both
age 7
name zhangsan
val ‘math‘: 60, ‘eng‘: 80

$ python test.py
only key
age
name
val
only val
7
zhangsan
‘math‘: 60, ‘eng‘: 80
both
age 7
name zhangsan
val ‘math‘: 60, ‘eng‘: 80

 Python 中set  

set() 函数创建一个无序不重复元素集，可进行关系测试，删除重复数据，还可以计算交集、差集、并集等。

 set 持有一系列元素，这一点和 list 很像，但是set的元素没有重复，而且是无序的，这点和 dict 的 key很像。

s = set([‘a‘,‘b‘,‘c‘])
print s   #输出set([‘a‘, ‘c‘, ‘b‘])
s = set([‘a‘,‘b‘,‘c‘,‘a‘])
print s   #输出set([‘a‘, ‘c‘, ‘b‘])

a = set([‘a‘,‘b‘,‘c‘])
b = set([‘a‘,‘b‘,‘c‘,‘d‘])
print a & b  #交集   输出set([‘a‘, ‘c‘, ‘b‘])
print a | b  #并集   输出set([‘a‘, ‘c‘, ‘b‘, ‘d‘])
print b - a  #差集   输出set([‘d‘])
print a - b  #差集   输出set([])