Python Basics (v)

1. Dictionaries

    Dict  using {} to represent    key value pair data  {Key:value}  Uniqueness

    Key  must be a hash   immutable data type that can be used as a key in the dictionary

      there is no limit to the value
    
Dict saved data is not saved in the order that we added it. It is stored in the order of the hash table. And the hash table is not sequential. Therefore, the slicing work is not possible.
It can only get the data in Dict by key.
　　

    Note: Key must be immutable (hashed). value is not required. Can save any type of data

2. Adding and deleting changes
　　
1) Increase

    Dic[key] = value

    Dic.setdefault (Key,value)   if the key exists in the dictionary without any action, add

                                Can be queried by key, without this key to return none
　　

    ====================================================================
2) Delete

    Pop (key)                    has a return value  that is returned by the deleted value
    Del Dic[key]
    Popitem ()                   random deletion
    Clear ()                     empty Dictionary
　　

    ======================================================================
3) Modify

    Dic[key] = value
    Dic.update (dictionary)
　　

    =======================================================================
4) Query

    Get (Key)
    Dic[key]
    For loop
    SetDefault (Key)

    =======================================================================

3. Other operations of the dictionary:

    Keys     gets to all the keys that exist in a high-imitated list

    Values   gets to all the values that exist in a high-imitated list

    Items    gets to all the key values in the form of a meta-ancestor exist in a highly imitated list

    Deconstruction:

          A, B = 1, 2

        A  , B = (up to)

        b  = [+]

4. Nesting of dictionaries:

        DIC = {
            ' Name ': ' Wang Feng ',
            ' Age ': 43,
            ' Wife ': {
                ' Name ': ' International Chapter ',
                ' Age ': 39,
                ' Salary ': 100000
            },
            ' Baby ': [
                {' name ': ' Big Bear ', ' age ': 18},
                {' name ': ' Bear II ', ' age ': 15},
            ]

        }

        dic[' baby '][0][' age ' = 19

        Print (DIC)

Python Basics (v)