some tips about python Four

import pickle

a_dict = {'da':111,2:[23,1,4],'23':{1:2,'d':'sad'}}

file = open('pickle_example.pickle','wb')

pickle.dump(a_dict,file)

file.close()

file = open('pickle_example.pickle','rb')

a_dict1 = pickle.load(file)

file.close()

print(a_dict1)

with open('pickle_example.pickle','wb') as file:
pickle.dump(a_dict,file)

with open('pickle_example.pickle','rb') as file: #不需要考虑关闭文件的问题，会自动关闭
a_dict1 = pickle.load(file)

print(a_dict1)

char_list = ['a','b','c','c','d','d','d']

print(set(char_list)) #重复的值，只保留一个，顺序会发生改变

print(type(set(char_list))) #打印类型

print(type({1:2}))

sentence = ‘Welcome Back to THis Tutorial'

print(set(sentence))

unique_char = set(char_list)

unique_char.add('x') #添加

print(unique_char)

unique_char.clear() #清除set

unique_char.remove('x') #清除，返回值为None，如果没有指定的元素，会报错

unique_char.discard('y') #如果没有指定的元素，不会报错

set1 = {'a','b','c'}

set2 = {'b','c','d'}

print(set1.difference(set2)) #打印set1里有，但是set2里面没有的元素，a

print(set1.intersection(set2)) #打印set1和set2的交集，b，c