【5.2】dict的常用方法

#!/user/bin/env python
# -*- coding:utf-8 -*-
import copy
a = {'zy': 123}

# clear
a.clear()
print(a)

# copy,返回浅拷贝
b = {'zy': {'school': 'hx'}}
new_dict = b.copy()
new_dict['zy']['school'] = 'hx1'
print(b)

# 深拷贝
c = {'zy': {'school': 'hx'}}
new_dict = copy.deepcopy(c)
new_dict['zy']['school'] = 'hx1'
print(c)

# fromkeys
new_list = ['zy1', 'zy2']
# fromkeys,第一个参数是一个可迭代对象，第二个参数是value的默认值
new_dict = dict.fromkeys(new_list, {'school': 'hx'})
print(new_dict)

# get
value = new_dict.get('zy', None)
print(value)

# item
for key, value in new_dict.items():
    print(key, value)

# setdefault, 在get的基础之上，如果在dict中没有get到值，那么不仅仅返回设置的默认值，还会将这个key，value加入到dict中
value = new_dict.setdefault('zy', None)
print(value)
print(new_dict)

# update,将key，value插入到dict中
new_dict.update({'zy111': 111})
new_dict.update(zy222=222, zy333=333)
new_dict.update([('zy444','444')])
new_dict.update((('zy555','555'),))
print(new_dict)

{}
{'zy': {'school': 'hx1'}}
{'zy': {'school': 'hx'}}
{'zy1': {'school': 'hx'}, 'zy2': {'school': 'hx'}}
None
zy1 {'school': 'hx'}
zy2 {'school': 'hx'}
None
{'zy1': {'school': 'hx'}, 'zy2': {'school': 'hx'}, 'zy': None}
{'zy1': {'school': 'hx'}, 'zy2': {'school': 'hx'}, 'zy': None, 'zy111': 111, 'zy222': 222, 'zy333': 333, 'zy444': '444', 'zy555': '555'}