字典的操作

Posted 2020-10-27 AllenZhang_(*^▽^*)

删除

del

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> del people[‘age‘]
>>> people
{‘kind‘: ‘beauty‘}

pop

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> people.pop(‘age‘)
‘22‘
>>> people
{‘kind‘: ‘beauty‘}

popitem 删除一个，不带参数(字典是无序的，不确定会删除哪个)

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> people.popitem()
(‘kind‘, ‘beauty‘)
>>> people
{‘age‘: ‘22‘}

增、改

setdefault 如果不存指定键在就新增，存在不做任何操作

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> people.setdefault(‘like‘, ‘sport‘)
‘sport‘
>>> people
{‘kind‘: ‘beauty‘, ‘like‘: ‘sport‘, ‘age‘: ‘22‘}
>>> people.setdefault(‘kind‘, ‘fool‘)
‘beauty‘
>>> people
{‘kind‘: ‘beauty‘, ‘like‘: ‘sport‘, ‘age‘: ‘22‘}

update 很常用，直接修改或新增

查

get  没取到为None（也可设置为其它）

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> like = people.get(‘like‘)
>>> like
>>> print like
None

in 是否存在该键（Python2里还有has_key也是相同用法，Python3里没有has_key）

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> print ‘kind‘ in people
True

>>> people = {‘kind‘: ‘beauty‘, ‘age‘: ‘22‘}
>>> print(‘age‘in people)
True

其它操作

items 转换为字典

>>> people
{‘kind‘: ‘beauty‘, ‘like‘: ‘sport‘, ‘age‘: ‘22‘}
>>> people.items()
dict_items([(‘kind‘, ‘beauty‘), (‘like‘, ‘sport‘), (‘age‘, ‘22‘)])

fromkeys 创建字典，所有的键共用一个值（修改一个，其它的都变，像浅copy）

>>> like = dict.fromkeys([‘sport‘, ‘singing‘, ‘dance‘], ‘666‘)
>>> like
{‘singing‘: ‘666‘, ‘sport‘: ‘666‘, ‘dance‘: ‘666‘}
>>> like[‘singing‘] = ‘yes‘
>>> like
{‘singing‘: ‘yes‘, ‘sport‘: ‘666‘, ‘dance‘: ‘666‘}

>>> lau = dict.fromkeys([‘C‘, ‘Java‘, ‘Python‘], [‘code‘, ‘yes‘])
>>> lau
{‘C‘: [‘code‘, ‘yes‘], ‘Python‘: [‘code‘, ‘yes‘], ‘Java‘: [‘code‘, ‘yes‘]}
>>> lau[‘Python‘][1] = ‘no‘
>>> lau
{‘C‘: [‘code‘, ‘no‘], ‘Python‘: [‘code‘, ‘no‘], ‘Java‘: [‘code‘, ‘no‘]}