1) join () is converted into a list of strings. Front jion to add '' which is what you what to splice
a=['a','s','f']
b=''.join(a)
print(b)===asf
2) split () cutting. String side field list
= A '= leaving card ah = = received, but refuse to'
B = a.split ( '=')
Print (B) == [ 'leave', 'card', 'received ah', 'but to the trash ']
3) Delete the problem
list and dict
Delete list can not be deleted directly in the loop
dict not change in the cycle length and size
The need to delete the contents kept in a list circulating this new list to delete the old list
4) set collection
Not repeat, disorderly, content hash, the most useful is repeated
5) formkes (a, b) to each element in a acquired and assembled into a new b dictionary returns
6) the depth of copies
Assignment: do not create a new object, both variables refer to the same object
Shallow Copy: Copy the contents of the first layer, to create a new object [:] Copy ()
Deep Copy: copy all the contents of all current and associated objects. deepcopy ()