Small pool and depth data copy

Small data pool

• What is a small data pool?

  • Python is a small data pool to increase the efficiency of one embodiment, a fixed data type using the same memory address
  • Support: str, int, bool

• Small data pool is doing?

  • id () View the memory address space of open space acquisition An address
  • Digital support small data pool range: -5 to 256
  • is: determining whether the same memory address two
  • ==: both sides of the equal sign is determined whether the value of the wanted copper

• String

  • Characters multiply when the total length can not exceed 20, to camp
  • Own definition string length is not limited, but must be an integral alphanumeric string underlined to camp
  • Special characters (except Chinese) defined a time, to camp
  • * 1 string, in fact assigned

• Block

  • A file, a module, a function, a class, each row is a terminal block, in the manner Python to store dictionaries
  • Digital, all reside
  • String
    • Multiplying the total length of not more than 20
    • Custom reside
    • Multiplier of 1 is assigned time
    • Python3.7 multiplication when the total length of not more than 4096

• Forced resident

• from sys import intern

  ​ a = intern(@@@@*20)

  ​ b = intern(@@@@*20)

  print (a is b) # themselves residing

set

• What is a collection?

  • Dictionary is a collection of no value, follow: unique, unordered, the elements required can hash (immutable)

  • Collection are variable and disorderly

  • The main role is to re

  • increase

    • s.update ( "3456") # iterations add
    • s.add()

  • delete

    • s.pop (): random delete # observed that, according to its own law a little, but not say
    • s.remove (): Delete by elements
    • s.clear (): Empty
    • del s: delete the entire collection

  • modify

    • Deleted plus is not changed

  • Other operations

    # print(s1 - s2)  #差集
    # print(s1 | s2)  #并集   (合集)
    # print(s1 & s2)  #交集
    # print(s1 ^ s2)  #对称差集  -- 反交集
    # print(s1 > s2)  # 超集   -- 父集
    # print(s1 < s2)  # 子集
    # 冻结集合(可变 转换成 不可变)  -- 更不常用
    # f_s = frozenset({1,2,3,4,5})
    # # dic = {f_s:"1"}
    # # print(dic)

Copy depth

• Copies of the depth of the law:

  Assignment: two variables in the same space is
  shallow copy: Review immutable data types, does not change, modify the variable data type, change
  deep copy: not modified variations