用python玩转数据|强大的数据结构和python扩展库

悠悠 2022-09-28 13:07 161阅读 0赞

**字典**

*  字典是一种映射类型（key-value对）。
 *  字典元素时无序的。

创建字典：

>>> aInfo = {
       'Wangdachui': 3000, 'Niuyun':2000, 'Linling':4500, 'Tianqi':8000}
    >>> info = [('Wangdachui',3000), ('Niuyun',2000), ('Linling',4500), ('Tianqi',8000)]
    >>> bInfo = dict(info)
    >>> cInfo = dict([['Wangdachui',3000], ['Niuyun',2000], ['Linling',4500], ['Tianqi',8000]])
    >>> dInfo = dict(Wangdachui=3000, Niuyun=2000, Linling=4500, Tianqi=8000)
    
    结果：
    {
       'Linling': 4500, 'Niuyun': 2000, 'Wangdachui': 3000, 'Tianqi': 8000}

dict.fromkeys(seq\[, value\]))：

seq = ('name', 'age', 'sex')
    
    dict = dict.fromkeys(seq)
    print "New Dictionary : %s" %  str(dict)
    
    dict = dict.fromkeys(seq, 10)
    print "New Dictionary : %s" %  str(dict)
    
    输出：
    New Dictionary : {
       'age': None, 'name': None, 'sex': None}
    New Dictionary : {
       'age': 10, 'name': 10, 'sex': 10}
    
    应用场景：eg为员工设置统一的默认工资。
    aDict = {}.fromkeys(('Wangdachui', 'Niuyun', 'Linling', 'Tianqi'),3000)
    输出：
    {
       'Tianqi': 3000, 'Wangdachui': 3000, 'Niuyun': 3000, 'Linling': 3000}

字典的基本操作：

>>> aInfo = {
       'Wangdachui': 3000, 'Niuyun':2000, 'Linling':4500, 'Tianqi':8000}
    >>> aInfo['Niuyun']
    5000
    >>> aInfo['Niuyun'] = 9999
    >>> aInfo
    {
       'Tianqi': 8000, 'Wangdachui': 3000, 'Linling': 4500, 'Niuyun': 9999}
    #注意此处！！字典可以通过键值直接增加元素！！List不可以哟！
    >>> aInfo['Fuyun'] = 1000
    >>> aInfo
    {
       'Tianqi': 8000, 'Fuyun': 1000, 'Wangdachui': 3000, 'Linling': 4500, 'Niuyun': 9999}
    >>> 'Mayun' in aInfo
    False
    >>> del aInfo
    >>> aInfo
    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    NameError: name 'aInfo' is not defined

update()方法：

>>> aInfo = {
       'Wangdachui': 3000, 'Niuyun':2000, 'Linling':4500}
    >>> bInfo = {
       'Wangdachui': 4000, 'Niuyun':9999, 'Wangzi':6000}
    >>> aInfo.update(bInfo)
    >>> aInfo
    输出：
    {
       'Wangzi': 6000, 'Linling': 4500, 'Niuyun': 9999, 'Wangdachui': 4000}

![SouthEast][]

字典的格式化字符串：

>>> aInfo = {
       'Wangdachui': 3000, 'Niuyun':2000, 'Linling':4500, 'Tianqi':8000}
    >>> for key in aInfo.keys():
    print 'name=%s, salary=%s' % (key, aInfo[key])
    >>> "Niuyun's salary is %(Niuyun)s." % aInfo
    "Niuyun's salary is 5000."
    
    >>> aInfo = {
       'Wangdachui': 3000, 'Niuyun':2000, 'Linling':4500, 'Tianqi':8000}
    >>> template = '''
    Welcome to the pay wall.
    Niuyun's salary is %(Niuyun)s.
    Wangdachui's salary is %(Wangdachui)s.
    '''
    >>> print template % aInfo
    Welcome to the pay wall.
    Niuyun's salary is 2000.
    Wangdachui's salary is 3000.

![SouthEast 1][]

![SouthEast 2][]

args1位置参数  
argst可变长位置参数  
argsd字典充当的可变长关键字参数  
![SouthEast 3][]

**集合**  
集合是一个无序不重复的元素的组合。

*  可变集合（set）
 *  不可变集合（fronzenset）

![SouthEast 4][]

[SouthEast]: /images/20220708/0ddbe4ce3520443e8bc8ff69e9fe14c8.png
[SouthEast 1]: /images/20220708/b64761a7f9c74f13a06562bcd3e9d257.png
[SouthEast 2]: /images/20220708/3f0c4be69e704bd6a7860c418b39a311.png
[SouthEast 3]: /images/20220708/f6534d99d67846ed81ed517c9dce4f0e.png
[SouthEast 4]: /images/20220708/23732217728c48119d82c759d645f0e5.png