python--Dictionary Types

Dictionary type ******************

2. Why do I need a dictionary type?
   >>> list1 = ["Name", "Age", "gender"]
   >>> list2 = ["Fentiao", 5, "male"]
   >>> Zip (list1, List2)
   Combine two lists with a zip built-in function, help (Zip)
   [(' Name ', ' Fentiao '), (' Age ', 5), (' Gender ', ' male ')]

   >>> list2[0]out[12]:
   In direct programming, there is no understanding that the first index represents a name
   ' Fentiao '
   >>> List2[name]
   Traceback (most recent):
   File "<stdin>", line 1, in <module>
   Typeerror:list indices must is integers, not str
   Therefore, the dictionary is the only type of mapping in Python, key-value (hash table), the Dictionary object is mutable, but the key must be an immutable object.

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4. Dictionary definition
   Simple dictionary creation

    >>> dic = {"name": "Fentiao", "Age": 5, "gender": "Male"}
    > >> Dic[0]  /Cannot extract value values by index
     Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     keyerror:0
     >>> dic["name"]    //find value values by key
     ' Fentiao '
   

   Built-in method: Fromkeys
        The key in the dictionary has the same value, default is None

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6. Access to Dictionary values
   Access directly via key

   
   

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8. Loop traversal access 650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M00/9C/19/wKiom1lsOsSRPM5wAACh_Jjy2H4942.png "title= "234520170717121628.png" style= "Float:none;" alt= "Wkiom1lsossrpm5waach_jjy2h4942.png"/>

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10. The addition of the dictionary Key-value
    Dic[key] = value through this operation, we will find that the dictionary is an unordered data type

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12. Updating the dictionary

    Dic.update (DIC1)

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13. Deletion of dictionaries
    Dic.pop (key) deletes the element of the dictionary based on the key value;

    >>> DIC
    {' Gender ': ' Male ', ' age ': 8, ' name ': ' Fentiao ', ' kind ': ' Cat '}
    >>> dic.pop ("kind")//pop-up Dictionary with key value "kind" and return element of that key
    ' Cat '
    >> DIC
    {' Gender ': ' Male ', ' age ': 8, ' name ': ' Fentiao '}
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    Dic.popitem () random Delete dictionary element, return (Key,value)

    >>>dic.popitem ()
    (' Gender ', ' male ')

    >>> DIC
    {' Age ': 5, ' name ': ' Fentiao '}
    Dic.clear () Delete all elements in the dictionary

    >>> dic.clear ()//delete all elements of the dictionary out[22]:
    >>> DIC
    {}
    del dic Delete the dictionary itself

    >>> del dic//delete entire dictionary
    >>> DIC
    Traceback (most recent):
    File "<stdin>", line 1, in <module>
    Nameerror:name ' dic ' is not defined

    
    

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14. Common methods of dictionaries
    Dict.get () If key exists in the dictionary, returns the corresponding value value

    >>>dic.get (' age ')
    5
    >>>dic.get (' Gender ')
    ' Male '
    Dic.keys () returns all key values of the dictionary

    >>>dic.keys ()
    [' Gender ', ' age ', ' name ']

    Dic.values () Returns all value values of the dictionary

    >>>dic.values ()
    [' Male ', 5, ' Fentiao ']

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    Dict.has_key () Whether a key value exists in the dictionary

    >>>dic.has_key (' name ')
    True
    >>>dic.has_key (' age ')
    True
    Dic.items ()

    >>>dic.items ()
    [(' Gender ', ' Male '), (' Age ', 5), (' Name ', ' Fentiao ')]

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15. Example: 650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M01/9C/19/wKiom1lsOsXCTbO_AAC6kwqe5dY318.png "title=" 234520170717121743.png "style=" Float:none; "alt=" Wkiom1lsosxctbo_aac6kwqe5dy318.png "/>

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python--Dictionary Types