[Python Basics-Dictionary]

Create dictionary

• Create dictionary directly

names = {'姓名': '阿肆', '年龄': 18, '爱好': '吃饭'}
print(names)

• Convert an object of sequence type into a dictionary through the function dict()

info = [('姓名', '阿肆'), ('年龄', 18,), ('爱好', '吃饭')]
print(type(info))
# 通过函数dict()将序列类型的对象转换为字典
info_1 = dict(info)
print(type(info_1))
print(info_1)

Note: Dictionary elements are unordered, so the output result is not unique

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
eLnfo = dict((('1',300),('2',390), ('3',900)))
print(info_2)
print(eLnfo)

-Create dictionary with method fromkeys()

gInfo = {}.fromkeys(('a','b','c'),"一gioa我哩giao")
print(gInfo)

Note: The elements in the dictionary are stored unordered and can be sorted using the sorted() function

Basic operations on dictionaries

• sort

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
print(sorted(info_2))

• Key value lookup

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
print(info_2['2'])

• Update some values_1

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
print(info_2)
info_2['1'] = 'I'
print(info_2)

Note: The keys in the dictionary cannot be updated (hashable). If you set a tuple as a key, you must restrict the elements of the tuple at all levels to be immutable.

• Add dictionary elements

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
info_2['4'] = 'giao'

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
info_2['4'] = 'giao'
info_2['5'] = ['阿 giao','红绿灯','阿远']

• Dictionary member judgment

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
print('3' in info_2)

• Delete a dictionary or a key value of a dictionary

del(info_2)

info_2 = dict([['1', "我"], ["2", "love"], ["3", 'YOU']])
print('3' in info_2)
info_2['4'] = 'giao'
info_2['5'] = ['阿 giao','红绿灯','阿远']
del(info_2['5'])

Dictionary built-in functions

function	Function
dict	Function to create dictionary
only (volume)	Returns the length of the dictionary (number of items)
hash(obj)	Determine whether obj is hashable

Dictionary methods
take several commonly used methods as examples

method	Function
keys()	Returns all key values ​​​​of the dictionary
painful()	$12
catheter	$1