Python dictionary operations

Starting today, I plan to write something every week to record my learning and mark it myself.

Dictionary is the most flexible built-in data structure in Python. A dictionary is an unordered collection (the order of the dictionary is random to quickly perform key lookups). Python uses an optimized hashing algorithm to find keys; a dictionary is similar to that in Java. map, but there are not as many types as map in java (HashMap, TreeMap, etc.).

Common dictionary operations

Assignment

D = {}  # 空字典
D = {"name": "zhangsan", "age": 23}  # 包含2个项目的字典
D = {"fruit": {"apple": 2, "orange": 1}}  # 嵌套
D = dict.fromkeys(["a", "b"], 2)  # {'a': 2, 'b': 2}
D = dict(zip(["name", "age"], ["zhangsan", '23']))  # {'age': '23', 'name': 'zhangsan'}

Value

name = D["name"]
age = D.get("age", 0)  # 如果不存在age属性就取值为0
keys = D.keys()  # 获取键
values = D.values()  # 获取value
if 'name' in D:
    print "name is in D"

Delete

D.pop('sex')  # 根据key删除
del D['name']  # 根据key删除

Other operations

D_1 = {"sex": "male"}
D.update(D_1)  # 合并dict