Python Base Three

//sixth day to study python(2016/8/7)

32. In python , there are have an special type dictionary , it is same with oc.

      such as:

      dicOne = {'wyg':'write code change world', 'roy':'you cand do it', 'tom':'just do it'}

      dicOne

      ->

      {'wyg':'write code change world', 'roy':'you cand do it', 'tom':'just do it'}

      dicOne['wyg']

      ->

      'wirte code change world'

      dicOne['wyg'] = 'believe youself'

      dicOne

      ->

      {'wyg':'believe youself', 'roy':'you cand do it', 'tom':'just do it'}

      dicTwo = dict(wyg = 'just do it', roy = 'you can do it')

      dicTwo

      ->

      {'wyg':'just do it', 'roy':'you can do it'}

      dicThree = dict((('r':'rrr'),('t':'ttt')))

      dicThree

      ->

      {'r':'rrr','t':'ttt'}

33. In python ,dictionary type we can use everywhere, so we should learn it more deeply.

      fromkeys()

      dict1 = {}

      dict1.fromkeys((1, 2, 3))

      ->

      {1:None, 2:None, 3:None}

      dict1.fromkeys((1,2,3),'Number')

      ->

      {1:'Number', 2:'Number', 3:'Number'}

      dict1.fromkeys((1,2,3),('one','two','three'))

      ->

      {1: ('one', 'two', 'three'), 2: ('one', 'two', 'three'), 3: ('one', 'two', 'three')}

      keys()

      dict1 = dict.fromkey(range(5),'roy')

      dict1

      ->

      {0:'roy',1:'roy',2:'roy',3:'roy',4:'roy'}

      for eachKey in dict1.keys():

           print(eachKey)

      ->

      0

      1

      2

      3

      4

      5

      values()

      for eachValue dict1.values():

           print(eachValue)

      ->

      roy

      roy

      roy

      roy

      roy

      items()

      for eachItem in dict1.items():

           print(eachItem)

      ->

      (0, 'roy')
      (1, 'roy')
      (2, 'roy')
      (3, 'roy')
      (4, 'roy')

      get()
      dict1.get(0)

      ->

      'roy'

      print(dict1.get(100))

      ->

      None

      dict1.get(1,'no keyvalue')

      ->

      'roy'

      dict1.get(100,'no keyvalue')

      ->

      'no keyvalue'

      in , not in (key)

      3 in dict1

      True

      100 in dict1

      False

      clear()

      dict1.clear()

      ->

      {}
      copy() (light copy)

      a = {1:'one',2:'two'}

      b = a.copy()

      c = a

      id(a)    id(b)   id(c)

      ->

     4346314824     4386886856     4346314824

     c[3] = 'three'

     a

    ->

    {1:'one',2:'two',3:'three'}

    b

    ->

    {1:'one',2:'two'}

    c

    ->

    {1:'one',2:'two',3:'three'}

    pop()
    a.pop(2)

    ->

    {1:'one',2:'three'}

    popitem()

    a.popitem()

    -> rand pop an object

    setdefault()

    a = {1:'one'}

    a.setdefault(2)

    a

    -> 

    {1:'one',2:None}

    a.setdefault(3,'three')

    {1:'one',2:None,3:'three}

    update()
    b = {'roy':'wyg'}

    a.update(b)

    ->

    {1:'one',2:None,3:'three,'roy':'wyg'}

34. we have learned dictionary ,now we learn set continue.

      num = {}

      type(num)

      <class 'dict' at 0x100229b60>

      num = {1,2,3}

      type(num)

     <class 'set' at 0x10022e420>

      in set ,all value is only but no support index. such as:

      num2 = {1,2,3,4,5,5,6}

      num2

      ->

      {1,2,3,4,5,6}

      num3 = set([1,2,3,4])

      num3

      ->

      {1,2,3,4}

       now how can remove repeat value from list

       such as:

       a = [1,2,3,4,5,5,6]

       b = []

       for each in a:

            if each not in b:

                      b.append(each)

       b

       ->

       [1,2,3,4,5,6]

       now that we have learned set ,how to achieve it by set

       a = list(set(a))

       ->

       [1,2,3,4,5,6]