1-datetime

#1-获取当前日期和时间from datetime import datetimenow = datetime.now() #当前时间print(now) #2015-05-18 16:28:07.198690#2-获取指定日期的时间dt = datetime(2015,4,19,12,20)print(dt) #2015-04-19 12:20:00#3-datetime转换为timestampdt = datetime(2015,4,19,12,20)print(dt.timestamp()) #1429417200.0 把datetime转换为timestamp#某些编程语言（如Java和JavaScript）的timestamp使用整数表示毫秒数，#这种情况下只需要把timestamp除以1000就得到Python的浮点表示方法。#4-timestamp转换为datetimet= 1429417200.0print(datetime.fromtimestamp(t)) #2015-04-19 12:20:00#5-str转换为datetimecday = datetime.strptime('2015-6-1 18:19:59', '%Y-%m-%d %H:%M:%S')print(cday) #2015-06-01 18:19:59#6-datetime转换为strnow = datetime.now()print(now.strftime('%a, %b %d %H:%M')) #Mon, May 05 16:28#7-datetime加减from datetime import datetime, timedeltanow = datetime.now()now + timedelta(days=2, hours=12)#8-本地时间转换为UTC时间

2-collections

#1-namedtuple 命名tuplefrom collections import namedtuplePoint = namedtuple('Point', ['x','y'])p = Point(1,2)print(p.y)#2-deque deque是为了高效实现插入和删除操作的双向列表，from collections import dequeq = deque(['a', 'b', 'c'])q.append('x')q.appendleft('y')print(q)#3-defaultdict#使用dict时，如果引用的Key不存在，就会抛出KeyError。#如果希望key不存在时，返回一个默认值，就可以用defaultdict：from collections import defaultdictdd = defaultdict(lambda: 'N/A')dd['key1'] = 'abc'#4-OrderedDict 按选插入就选输出from collections import OrderedDictod = OrderedDict([('a', 1), ('b', 2), ('c', 3)])#5-Counter 统计字符出现的个数：from collections import Counterc = Counter()for ch in 'programming':    c[ch] = c[ch] + 1print(c)