python 笔记4

 字典的运算 可变数据类型

1、get  获取值

s_info ={
         "m":{ "lots":1,
               "max_lot":1024,
                "step":0.18 ,
                "p_id":"m"

              },
          "a": {"lots": 1 ,
                "max_lot": 1024 ,
                "step": 0.28 ,
                "p_id": "a"

                }
}
print(s_info["a"]["p_id"])
print(s_info.get("m","123"))
print(s_info["a"].get("p_id"))
print(s_info.get("m").get("p_id"))
2、更新值  update

s_info.update({"l":9})
print(s_info)
s_info["a"].update({"lots":62})
print(s_info["a"])
s_info["m"]["保证金"] = 6000
print(s_info["m"])
3、pop 删除值

print(s_info["m"].pop("保证金"))
print(s_info["m"])
4、clear

s_info["a"].clear()
print(s_info)
5 for 循环

for key in s_info.keys():
    print(key)
6、key and values

for k in s_info["m"].values():
    print(k)
7。 item

for v in s_info["m"].items():
    print(v)

for h,v in s_info["m"].items():
    print(h,v)

for j in list(s_info):
     if j=="a":
         s_info.pop('a')
print(list(s_info))

集合

trade ={1,2,3,4,5,6}
a_trader={1,2,3}
new_trade =trade -a_trader // 求集合差集
print(new_trade)

for ta in new_trade:
    print(ta)
    a_trader.add(ta) 
print(a_trader)      // 集合合

nan
代表任意值

m = float('nan')    
print(m+5)         nan 不与自身相等， 返回false