8. 数据类型

8.1. datetime

8.1.1. timedelta

class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)

样例：

In [9]: from datetime import timedelta

In [10]: year = timedelta(days=365,hours=23,minutes=50,seconds=600)

In [11]: year.total_seconds()
Out[11]: 31622400.0

In [12]: year
Out[12]: datetime.timedelta(366)

In [13]: print(year)
366 days, 0:00:00

8.1.2. date

样例：

In [15]: from datetime import date

In [16]: date.min
Out[16]: datetime.date(1, 1, 1)

In [17]: date.max
Out[17]: datetime.date(9999, 12, 31)

In [21]: today = date.today()

In [22]: today
Out[22]: datetime.date(2018, 2, 11)

# 日期构造
In [24]: another_day = date(today.year,5,14)

In [25]: another_day
Out[25]: datetime.date(2018, 5, 14)

# 日期差值
In [26]: times = abs(today - another_day)

In [27]: type(times)
Out[27]: datetime.timedelta

In [28]: times.total_seconds
Out[28]: <function timedelta.total_seconds>

In [29]: times.total_seconds()
Out[29]: 7948800.0

# 日期转字符串的
In [30]: today.strftime("%Y-%m-%d")
Out[30]: '2018-02-11'

8.1.3. datetime

样例：

In [33]: d = date(2018,7,14)

In [34]: d
Out[34]: datetime.date(2018, 7, 14)

In [35]: t = time(12,30)

# 日期和时间构造一个datetime
In [36]: datetime.combine(d,t)
Out[36]: datetime.datetime(2018, 7, 14, 12, 30)

# 当前时间
In [37]: datetime.now()
Out[37]: datetime.datetime(2018, 2, 11, 15, 23, 19, 986889)

# utc时间，北京和utc时区差8个小时
In [38]: datetime.utcnow()
Out[38]: datetime.datetime(2018, 2, 11, 7, 23, 26, 978965)

In [39]: now = datetime.utcnow()

# 日期转字符串
In [41]: now.strftime("%Y-%m-%d %H:%M:%S")
Out[41]: '2018-02-11 07:23:39'

In [43]: now_str = '2018-02-11 07:23:39'

# 字符串转日期
In [44]: datetime.strptime(now_str,"%Y-%m-%d %H:%M:%S")
Out[44]: datetime.datetime(2018, 2, 11, 7, 23, 39)

8.1.4. time

样例：

In [46]:  from datetime import time

In [47]:  dt = time(hour=12, minute=34, second=56, microsecond=0)

# 指定下显示的精度程度
In [48]: dt.isoformat(timespec='microseconds')
Out[48]: '12:34:56.000000'

# 默认的，只是显示，时分秒
In [49]: dt.isoformat(timespec='auto')
Out[49]: '12:34:56'

8.1.5. 格式控制

日期格式控制符

8.2. calendar

提供日历功能

8.3. collectons

提供容器数据类型

8.3.1. ChainMap

提供用于快速链接多个映射，以便将它们视为单个单元。 它通常比创建新字典和运行多个update()调用要快得多。

样例：

In [53]: from collections import ChainMap

In [54]: c= ChainMap()

In [55]: d = c.new_child()

In [56]: e = c.new_child()

In [57]: e.maps[0]
Out[57]: {}

In [58]: e.maps[-1]
Out[58]: {}

In [59]: e.parents
Out[59]: ChainMap({})

In [60]: d['x'] = "abc"

In [61]: d
Out[61]: ChainMap({'x': 'abc'}, {})

In [62]: list(d)
Out[62]: ['x']

In [63]: d.items()
Out[63]: ItemsView(ChainMap({'x': 'abc'}, {}))

In [64]: dict(d)
Out[64]: {'x': 'abc'}

8.3.2. Counter

计数功能

# 导入
In [1]: from collections import Counter

# 构造新对象
In [2]: cnt=Counter()

# 开始计数
In [4]: for word in ["read","blue","green","blue","blue"]:
...:     cnt[word]+=1
...:
# 查看
In [5]: cnt
Out[5]: Counter({'blue': 3, 'green': 1, 'read': 1})
# 访问指定key
In [6]: cnt["blue"]
Out[6]: 3
# 直接设置
In [8]: cnt["yellow"] = 2
# 转化为dict
In [9]: dict(cnt)
Out[9]: {'blue': 3, 'green': 1, 'read': 1, 'yellow': 2}

# 查看所有元素
In [14]: list(cnt.elements())
Out[14]: ['read', 'blue', 'blue', 'blue', 'green', 'yellow', 'yellow']

# 减法
In [15]: c = Counter(a=4, b=2, c=0, d=-2)

In [16]: d = Counter(a=1, b=2, c=3, d=4)

In [17]: c.subtract(d)

In [18]: c
Out[18]: Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6})

# 个数总和
In [20]: sum(c.values())
Out[20]: -6

8.3.3. deque

队列

常用方法：

# 导入
In [23]: from collections import deque

# 初始化
In [24]: d=deque("abc")

# 查看
In [25]: d
Out[25]: deque(['a', 'b', 'c'])

# 追加
In [26]: d.append("d")

# 查看
In [27]: d
Out[27]: deque(['a', 'b', 'c', 'd'])

# 左侧追加
In [28]: d.appendleft("0")

# 查看
In [29]: d
Out[29]: deque(['0', 'a', 'b', 'c', 'd'])

# 特定元素的个数
In [30]: d.count("0")
Out[30]: 1

# 批量追加
In [31]: d.extend("ef")

# 查看
In [32]: d
Out[32]: deque(['0', 'a', 'b', 'c', 'd', 'e', 'f'])

# 特定位置插入
In [33]: d.insert(4 ,"a")

# 查看
In [34]: d
Out[34]: deque(['0', 'a', 'b', 'c', 'a', 'd', 'e', 'f'])

# 右侧去除
In [35]: d.pop()
Out[35]: 'f'

# 查看
In [36]: d
Out[36]: deque(['0', 'a', 'b', 'c', 'a', 'd', 'e'])

# 左侧弹出
In [37]: d.popleft()
Out[37]: '0'

# 查看
In [38]: d
Out[38]: deque(['a', 'b', 'c', 'a', 'd', 'e'])

# 滚动2下，就是右边的元素放到第一个位置，在删除他原来的
In [39]: d.rotate(2)

# 查看
In [40]: d
Out[40]: deque(['d', 'e', 'a', 'b', 'c', 'a'])

获取到指定文件最后几行

In [44]: def tail (filename ,n=10):
    ...:     with open(filename) as f:
    ...:         return deque(f,n)
    ...:

8.3.4. defaultdict

默认字典，就是在原有字典的基础上提供默认值。

In [46]: from collections import defaultdict

In [47]: s = "zhaojiedi"

In [48]: d = defaultdict(int)

In [49]: for k in s:
    ...:     d[k]+=1
    ...:

In [50]: d
Out[50]:
defaultdict(int,
            {'a': 1, 'd': 1, 'e': 1, 'h': 1, 'i': 2, 'j': 1, 'o': 1, 'z': 1})

In [52]: d.items()
Out[52]: dict_items([('z', 1), ('h', 1), ('a', 1), ('o', 1), ('j', 1), ('i', 2), ('e', 1), ('d', 1)])

上面使用defaultdict指定int参数，如果没有值的话，会自动获取int的默认值0的。

8.3.5. namedtuple

给元组提供了名字的扩展

In [53]: from collections import namedtuple

In [54]: Point=namedtuple('Point',['x','y'])

In [55]: p=Point(11,2)

In [56]: p
Out[56]: Point(x=11, y=2)

In [57]: p.x +p.y
Out[57]: 13

In [58]: p[0] + p[1]
Out[58]: 13

# list 元素转化元组
In [59]: t=[1,2]

In [60]: Point._make(t)
Out[60]: Point(x=1, y=2)

# 命名元组转化有序字典
In [62]: p= Point(x=11,y=2)

In [63]: p._asdict()
Out[63]: OrderedDict([('x', 11), ('y', 2)])

# 获取字段
In [64]: p._fields
Out[64]: ('x', 'y')

# 获取属性值
In [66]: getattr(p,'x')
Out[66]: 11

8.3.6. OrderedDict

有序字典与普通词典一样，但它们记住插入项的顺序。在遍历一个有序字典时，这些项将按其第一次添加的顺序返回。

# 导入
In [67]: from collections import OrderedDict

In [68]: d= {'banana':3 , 'appale': 4 , 'orange':2}

# 根据元素的key来排序
In [69]: e = OrderedDict(sorted(d.items(),key=lambda t:t[0]))

In [70]: e
Out[70]: OrderedDict([('appale', 4), ('banana', 3), ('orange', 2)])

# 根据元素的value来排序
In [71]: f = OrderedDict(sorted(d.items(),key=lambda t:t[1]))

In [72]: f
Out[72]: OrderedDict([('orange', 2), ('banana', 3), ('appale', 4)])

8.4. collections.abc

这个模块提供抽象基类，可以用来测试是否一个类提供了一个特定的接口；

8.5. heapq

这个模块提供了一个堆队列算法的实现，也称为优先级队列算法。

# 导入
In [87]: from heapq import heappush,heappop

In [88]: h=[]

# 添加一个元组
In [89]: heappush(h,(5,'write code'))

In [90]: h
Out[90]: [(5, 'write code')]

# 在加一个
In [91]: heappush(h,(7,'write book'))

In [92]: h
Out[92]: [(5, 'write code'), (7, 'write book')]

# 弹出一个
In [93]: heappop(h)
Out[93]: (5, 'write code')

# 查看
In [94]: h
Out[94]: [(7, 'write book')]

8.6. bisect

此模块提供了支持以排序的顺序维护列表，而不必在每次插入之后对列表进行排序。

样例：

In [110]: from bisect import bisect , bisect_left

In [111]: def grade(score, breakpoints=[60, 70, 80, 90], grades='FDCBA'):
    ...:     i = bisect(breakpoints, score)
    ...:     return grades[i]
    ...:

In [112]:

In [112]: [grade(score) for score in [33, 99, 77, 70, 89, 90, 100]]
Out[112]: ['F', 'A', 'C', 'C', 'B', 'A', 'A']

上面的使用4 个break point 将区间划分为5个， 每个对应一个等级，使用bisect去查找对应索引。

8.7. array

这个模块定义了一个可以紧凑地表示基本值数组的对象类型：字符、整数、浮点数。

8.8. weakref

这个模块允许Python程序员创建对象的弱引用

8.9. types

此模块定义实用工具函数，以帮助动态创建新类型。

8.10. copy

此模块提供深copy和浅copy功能

样例：

In [113]: class Point:
    ...:     pass
    ...:

In [114]: p= Point()

In [116]: import copy

In [117]: p2 =copy.copy(p)

In [119]: p3 = copy.deepcopy(p)

8.11. pprint

数据显示美化打印

方法： pprint.pprint(object, stream=None, indent=1, width=80, depth=None, *, compact=False)

>>> import json
>>> import pprint
>>> from urllib.request import urlopen
>>> with urlopen('http://pypi.python.org/pypi/Twisted/json') as url:
...     http_info = url.info()
...     raw_data = url.read().decode(http_info.get_content_charset())
>>> project_info = json.loads(raw_data)

>>> pprint.pprint(project_info)
{'info': {'_pypi_hidden': False,
        '_pypi_ordering': 125,
        'author': 'Glyph Lefkowitz',
        'author_email': 'glyph@twistedmatrix.com',
        'bugtrack_url': '',
        'cheesecake_code_kwalitee_id': None,
        'cheesecake_documentation_id': None,
        'cheesecake_installability_id': None,
        'classifiers': ['Programming Language :: Python :: 2.6',
                        'Programming Language :: Python :: 2.7',
                        'Programming Language :: Python :: 2 :: Only'],
        'description': 'An extensible framework for Python programming, with '
                        'special focus\r\n'
                        'on event-based network programming and multiprotocol '
                        'integration.',
        'docs_url': '',
        'download_url': 'UNKNOWN',
        'home_page': 'http://twistedmatrix.com/',
        'keywords': '',
        'license': 'MIT',
        'maintainer': '',
        'maintainer_email': '',
        'name': 'Twisted',
        'package_url': 'http://pypi.python.org/pypi/Twisted',
        'platform': 'UNKNOWN',
        'release_url': 'http://pypi.python.org/pypi/Twisted/12.3.0',
        'requires_python': None,
        'stable_version': None,
        'summary': 'An asynchronous networking framework written in Python',
        'version': '12.3.0'},
'urls': [{'comment_text': '',
        'downloads': 71844,
        'filename': 'Twisted-12.3.0.tar.bz2',
        'has_sig': False,
        'md5_digest': '6e289825f3bf5591cfd670874cc0862d',
        'packagetype': 'sdist',
        'python_version': 'source',
        'size': 2615733,
        'upload_time': '2012-12-26T12:47:03',
        'url': 'https://pypi.python.org/packages/source/T/Twisted/Twisted-12.3.0.tar.bz2'},
        {'comment_text': '',
        'downloads': 5224,
        'filename': 'Twisted-12.3.0.win32-py2.7.msi',
        'has_sig': False,
        'md5_digest': '6b778f5201b622a5519a2aca1a2fe512',
        'packagetype': 'bdist_msi',
        'python_version': '2.7',
        'size': 2916352,
        'upload_time': '2012-12-26T12:48:15',
        'url': 'https://pypi.python.org/packages/2.7/T/Twisted/Twisted-12.3.0.win32-py2.7.msi'}]}

>>> pprint.pprint(project_info, depth=2)
{'info': {'_pypi_hidden': False,
        '_pypi_ordering': 125,
        'author': 'Glyph Lefkowitz',
        'author_email': 'glyph@twistedmatrix.com',
        'bugtrack_url': '',
        'cheesecake_code_kwalitee_id': None,
        'cheesecake_documentation_id': None,
        'cheesecake_installability_id': None,
        'classifiers': [...],
        'description': 'An extensible framework for Python programming, with '
                        'special focus\r\n'
                        'on event-based network programming and multiprotocol '
                        'integration.',
        'docs_url': '',
        'download_url': 'UNKNOWN',
        'home_page': 'http://twistedmatrix.com/',
        'keywords': '',
        'license': 'MIT',
        'maintainer': '',
        'maintainer_email': '',
        'name': 'Twisted',
        'package_url': 'http://pypi.python.org/pypi/Twisted',
        'platform': 'UNKNOWN',
        'release_url': 'http://pypi.python.org/pypi/Twisted/12.3.0',
        'requires_python': None,
        'stable_version': None,
        'summary': 'An asynchronous networking framework written in Python',
        'version': '12.3.0'},
'urls': [{...}, {...}]}

8.12. reprlib

reprlib模块提供了对生成的字符串的大小限制生产对象表示的一种手段

8.13. enum

枚举

In [135]: from enum import Enum,auto

In [137]: class Color(Enum):
    ...:     RED=1
    ...:     GREEN =2
    ...:     BLUE =auto()
    ...:

In [138]: print(Color.RED)
Color.RED

In [139]: print(Color.RED.name)
RED

In [140]: print(Color.RED.value)
1

# 判断
In [141]: Color.RED == Color(1)
Out[141]: True

# 给枚举加唯一条件
In [142]: from enum import Enum , unique

In [143]: @unique
    ...: class MIsstake(Enum):
    ...:     one=1
    ...:     two=2
    ...:     three=3
    ...:     four=3
    ...:
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-143-8f8798c8b548> in <module>()
    1 @unique
----> 2 class MIsstake(Enum):
    3     one=1
    4     two=2
    5     three=3

D:\Users\Administrator\Anaconda3\lib\enum.py in unique(enumeration)
    832                 ["%s -> %s" % (alias, name) for (alias, name) in duplicates])
    833         raise ValueError('duplicate values found in %r: %s' %
--> 834                 (enumeration, alias_details))
    835     return enumeration
    836

ValueError: duplicate values found in <enum 'MIsstake'>: four -> three

# 遍历
In [145]: [ name for name, member in Color.__members__.items() ]
Out[145]: ['RED', 'GREEN', 'BLUE']

8.13.1. IntEnum

整型枚举

In [146]: from enum import IntEnum
    ...: class Shape(IntEnum):
    ...:     circle =1
    ...:     square =2
    ...:

In [147]: Shape.circle ==1
Out[147]: True

8.13.2. IntFlag

整型标记

In [150]: class Perm(IntFlag):
    ...:     R =4
    ...:     W =2
    ...:     X =1
    ...:
    ...:

In [151]: Perm.R
Out[151]: <Perm.R: 4>

In [152]: Perm.R  ==4
Out[152]: True

In [153]: Perm.R | Perm.W
Out[153]: <Perm.R|W: 6>

In [154]: Perm.R | Perm.W  ==6
Out[154]: True

8.14. Flag

标记

In [160]: from enum import Flag
    ...: class Color(Flag):
    ...:     red=auto()
    ...:     blue=auto()
    ...:     green=auto()
    ...:

In [161]: Color.red
Out[161]: <Color.red: 1>

In [162]: Color.red ==1
Out[162]: False

In [163]: Color.blue
Out[163]: <Color.blue: 2>

In [164]: Color.green
Out[164]: <Color.green: 4>

使用Flag，每个item都是按照1，2，4，8，16这样的值。

这种flag的主要用于后续有异或运算的情况下。