Python学习笔记(4)：字典

1. 字典的基本操作

1.1 创建一个字典

doer_0 = {"name":"hsy","gender":"male","age":22} #空字典doer_0 = {}
print(doer_0["name"])
hsy
print(doer_0["gender"])
male
print(doer_0["age"])
22

1.2 增加键值对

doer_0["hobby"] = "bioinformatics"
print(doer_0)
{'name': 'hsy', 'gender': 'male', 'age': 22, 'hobby': 'bioinformatics'}

1.3 修改键的值

doer_0["hobby"] = "Python"
print(doer_0)
{'name': 'hsy', 'gender': 'male', 'age': 22, 'hobby': 'Python'}

1.4 删除键值对

del doer_0["hobby"]
print(doer_0)
{'name': 'hsy', 'gender': 'male', 'age': 22}

1.5 类似对象组成的字典

跟Perl中的哈希表一样

doers_performance = {"hsy1":"good","hsy2":"very good"}
print(doers_performance)
{'hsy1': 'good', 'hsy2': 'very good'}

2. 遍历字典

遍历键值对

for key,value in doer_0.items():
    print(key)
    print(str(value) + "\n------")
    
name
hsy
------
gender
male
------
age
22
------

遍历键

for key in doer_0.keys():
    print(key + "\n------")    
    
name
------
gender
------
age
------

#按顺序遍历
for key in sorted(doer_0.keys()):
    print(key + "\n------")
    
age
------
gender
------
name
------

遍历值，可使用方法values()；当值列表含有重复元素时，可使用函数set()去重显示。

3. 字典的嵌套

3.1 在列表中存储字典

doer_1 = {'name':'xiaoming','gender':'male','age':12}
print(doer_1)
{'name': 'xiaoming', 'gender': 'male', 'age': 12}
doers = [doer_0,doer_1]
print(doers)
[{'name': 'hsy', 'gender': 'male', 'age': 22}, {'name': 'xiaoming', 'gender': 'male', 'age': 12}]
for doer in doers:
    print(doer)
    
{'name': 'hsy', 'gender': 'male', 'age': 22}
{'name': 'xiaoming', 'gender': 'male', 'age': 12}

3.2 在字典中存储列表

3.3 在字典中存储字典