python标准库学习4
>>> os.environ["HOME"] 'C:\\Users\\Administrator' >>> os.getcwd() #获得当前的目录 'D:\\new' >>> os.getenv("QTDIR") #获取环境变量的值 'D:\\vs2010-qt-src-4.7.4\\qt-src-4.7.4' os.putenv(varname, value) #设置环境变量的值 os.mkdir(path[, mode]) >>> os.mkdir("aa") >>> os.rmdir("aa") >>>os.makedirs("aa\\bb\\cc") 多级目录 os.removedirs(path)¶ os.remove("d:\\new\\hello.txt") #删除文件，如果是目录的话，出错 os.rename("test.txt","a.txt") random.randint(a, b) Return a random integer N such that a <= N <= b. random.choice(seq) Return a random element from the non-empty sequence seq. If seq is empty, raises IndexError. random.random() Return the next random floating point number in the range [0.0, 1.0). random.shuffle(x[, random]) 随机排序序列 random.uniform(a, b)¶返回a<=N<=b之间的浮点数 random.randrange([start], stop[, step])想当于choice(range(start, stop, step)) >>> random.random() # Random float x, 0.0 <= x < 1.0 0.37444887175646646 >>> random.uniform(1, 10) # Random float x, 1.0 <= x < 10.0 1.1800146073117523 >>> random.randint(1, 10) # Integer from 1 to 10, endpoints included 7 >>> random.randrange(0, 101, 2) # Even integer from 0 to 100 26 >>> random.choice('abcdefghij') # Choose a random element 'c' >>> items = [1, 2, 3, 4, 5, 6, 7] >>> random.shuffle(items) >>> items [7, 3, 2, 5, 6, 4, 1] >>> random.sample([1, 2, 3, 4, 5], 3) # Choose 3 elements [4, 1, 5] >>> datetime.MAXYEAR 9999 >>> datetime.MINYEAR 1 >>> a=datetime.date(2011,2,1) >>> a.today() datetime.date(2011, 11, 26) >>> a.year 2011 >>> a.month 2 >>> a.day 1 >>> import time >>> from datetime import date >>> today = date.today() >>> today datetime.date(2007, 12, 5) >>> my_birthday = date(today.year, 6, 24) >>> if my_birthday < today: ... my_birthday = my_birthday.replace(year=today.year + 1) >>> my_birthday datetime.date(2008, 6, 24) >>> time_to_birthday = abs(my_birthday - today) #计算日期之差 >>> time_to_birthday.days 202 >>> datetime.now() #当前时间 datetime.datetime(2011, 11, 26, 10, 40, 10, 283000) >>> datetime.utcnow() datetime.datetime(2011, 11, 26, 2, 40, 34, 809000) >>> a=date(2005,7,14) #日期和时间进行合并 >>> t=time(12,30,12) >>> datetime.combine(a,t) datetime.datetime(2005, 7, 14, 12, 30, 12) >>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M") >>> dt datetime.datetime(2006, 11, 21, 16, 30) >>> from datetime import timedelta, datetime, tzinfo >>> class GMT1(tzinfo): ... def __init__(self): # DST starts last Sunday in March ... d = datetime(dt.year, 4, 1) # ends last Sunday in October ... self.dston = d - timedelta(days=d.weekday() + 1) ... d = datetime(dt.year, 11, 1) ... self.dstoff = d - timedelta(days=d.weekday() + 1) ... def utcoffset(self, dt): ... return timedelta(hours=1) + self.dst(dt) ... def dst(self, dt): ... if self.dston <= dt.replace(tzinfo=None) < self.dstoff: ... return timedelta(hours=1) ... else: ... return timedelta(0) ... def tzname(self,dt): ... return "GMT +1" ... >>> class GMT2(tzinfo): ... def __init__(self): ... d = datetime(dt.year, 4, 1) ... self.dston = d - timedelta(days=d.weekday() + 1) ... d = datetime(dt.year, 11, 1) ... self.dstoff = d - timedelta(days=d.weekday() + 1) ... def utcoffset(self, dt): ... return timedelta(hours=1) + self.dst(dt) ... def dst(self, dt): ... if self.dston <= dt.replace(tzinfo=None) < self.dstoff: ... return timedelta(hours=2) ... else: ... return timedelta(0) ... def tzname(self,dt): ... return "GMT +2" ... >>> gmt1 = GMT1() >>> # Daylight Saving Time >>> dt1 = datetime(2006, 11, 21, 16, 30, tzinfo=gmt1) >>> dt1.dst() datetime.timedelta(0) >>> dt1.utcoffset() datetime.timedelta(0, 3600) >>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=gmt1) >>> dt2.dst() datetime.timedelta(0, 3600) >>> dt2.utcoffset() datetime.timedelta(0, 7200) >>> # Convert datetime to another time zone >>> dt3 = dt2.astimezone(GMT2()) >>> dt3 # doctest: +ELLIPSIS datetime.datetime(2006, 6, 14, 14, 0, tzinfo=<GMT2 object at 0x...>) >>> dt2 # doctest: +ELLIPSIS datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>) >>> dt2.utctimetuple() == dt3.utctimetuple() True class datetime.time(hour[, minute[, second[, microsecond[, tzinfo]]]]) >>> a=time(10,46,12) >>> a.min datetime.time(0, 0) >>> a.max datetime.time(23, 59, 59, 999999) >>> a.hour 10 >>> a.minute 46 >>> a.second 12 >>> a.microsecond 0 class collections.Counter([iterable-or-mapping]) A Counter is a dict subclass for counting hashable objects. >>> # Tally occurrences of words in a list >>> cnt = Counter() >>> for word in ['red', 'blue', 'red', 'green', 'blue', 'blue']: ... cnt[word] += 1 >>> cnt Counter({'blue': 3, 'red': 2, 'green': 1}) >>> # Find the ten most common words in Hamlet >>> import re >>> words = re.findall('\w+', open('hamlet.txt').read().lower()) >>> Counter(words).most_common(10) [('the', 1143), ('and', 966), ('to', 762), ('of', 669), ('i', 631), ('you', 554), ('a', 546), ('my', 514), ('hamlet', 471), ('in', 451)] >>> c = Counter(['eggs', 'ham']) >>> c['bacon'] # count of a missing element is zero 0 >>> c['sausage'] = 0 # counter entry with a zero count >>> del c['sausage'] # del actually removes the entry >>> c = Counter(a=4, b=2, c=0, d=-2) >>> list(c.elements()) ['a', 'a', 'a', 'a', 'b', 'b'] most_common([n]) #出现次数最多的n个 >>> Counter('abracadabra').most_common(3) [('a', 5), ('r', 2), ('b', 2)] >>> c = Counter(a=4, b=2, c=0, d=-2) >>> d = Counter(a=1, b=2, c=3, d=4) >>> c.subtract(d) Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6}) >>> c = Counter(a=4, b=2, c=0, d=-2) >>> sum(c.values()) # total of all counts 4 >>> list(c) ['a', 'c', 'b', 'd'] >>> set(c) set(['a', 'c', 'b', 'd']) >>> dict(c) {'a': 4, 'c': 0, 'b': 2, 'd': -2} >>> c.items() [('a', 4), ('c', 0), ('b', 2), ('d', -2)] >>> c.most_common()[:-2:-1] # c.most_common()[:-n:-1] n least #common elements [('d', -2)] >>> c+=Counter() >>> c Counter({'a': 4, 'b': 2}) >>> c.clear() >>> c Counter() >>> c = Counter(a=3, b=1) >>> d = Counter(a=1, b=2) >>> c + d # add two counters together: c[x] + d[x] Counter({'a': 4, 'b': 3}) >>> c - d # subtract (keeping only positive counts) Counter({'a': 2}) >>> c & d # intersection: min(c[x], d[x]) Counter({'a': 1, 'b': 1}) >>> c | d # union: max(c[x], d[x]) Counter({'a': 3, 'b': 2}) >>> from collections import deque >>> d = deque('ghi') # make a new deque with three items >>> for elem in d: # iterate over the deque's elements ... print elem.upper() G H I >>> d.append('j') # add a new entry to the right side >>> d.appendleft('f') # add a new entry to the left side >>> d # show the representation of the deque deque(['f', 'g', 'h', 'i', 'j']) >>> d.pop() # return and remove the rightmost item 'j' >>> d.popleft() # return and remove the leftmost item 'f' >>> list(d) # list the contents of the deque ['g', 'h', 'i'] >>> d[0] # peek at leftmost item 'g' >>> d[-1] # peek at rightmost item 'i' >>> list(reversed(d)) # list the contents of a deque in reverse ['i', 'h', 'g'] >>> 'h' in d # search the deque True >>> d.extend('jkl') # add multiple elements at once >>> d deque(['g', 'h', 'i', 'j', 'k', 'l']) >>> d.rotate(1) # right rotation >>> d deque(['l', 'g', 'h', 'i', 'j', 'k']) >>> d.rotate(-1) # left rotation >>> d deque(['g', 'h', 'i', 'j', 'k', 'l']) >>> deque(reversed(d)) # make a new deque in reverse order deque(['l', 'k', 'j', 'i', 'h', 'g']) >>> d.clear() # empty the deque >>> d.pop() # cannot pop from an empty deque Traceback (most recent call last): File "<pyshell#6>", line 1, in -toplevel- d.pop() IndexError: pop from an empty deque >>> d.extendleft('abc') # extendleft() reverses the input order >>> d deque(['c', 'b', 'a']) def tail(filename, n=10): 'Return the last n lines of a file' return deque(open(filename), n) def moving_average(iterable, n=3): # moving_average([40, 30, 50, 46, 39, 44]) --> 40.0 42.0 45.0 43.0 # http://en.wikipedia.org/wiki/Moving_average it = iter(iterable) d = deque(itertools.islice(it, n-1)) d.appendleft(0) s = sum(d) for elem in it: s += elem - d.popleft() d.append(elem) yield s / float(n) def delete_nth(d, n): d.rotate(-n) d.popleft() d.rotate(n) class collections.defaultdict([default_factory[, ...]]) >>> s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)] >>> d = defaultdict(list) >>> for k, v in s: ... d[k].append(v) ... >>> d.items() [('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])] >>> d = {} >>> for k, v in s: ... d.setdefault(k, []).append(v) ... >>> d.items() [('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])] >>> s = 'mississippi' >>> d = defaultdict(int) >>> for k in s: ... d[k] += 1 ... >>> d.items() [('i', 4), ('p', 2), ('s', 4), ('m', 1)] >>> s = [('red', 1), ('blue', 2), ('red', 3), ('blue', 4), ('red', 1), ('blue', 4)] >>> d = defaultdict(set) >>> for k, v in s: ... d[k].add(v) ... >>> d.items() [('blue', set([2, 4])), ('red', set([1, 3]))] >>> def heapsort(iterable): ... 'Equivalent to sorted(iterable)' ... h = [] ... for value in iterable: ... heappush(h, value) ... return [heappop(h) for i in range(len(h))] ... >>> heapsort([1, 3, 5, 7, 9, 2, 4, 6, 8, 0]) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> h = [] >>> heappush(h, (5, 'write code')) >>> heappush(h, (7, 'release product')) >>> heappush(h, (1, 'write spec')) >>> heappush(h, (3, 'create tests')) >>> heappop(h) (1, 'write spec') #coding=utf-8 #堆的实例 from heapq import heappush, heappop, heappushpop, heapify, heapreplace, nlargest,\ nsmallest heap=[] heappush(heap,"A"); heappush(heap,"C"); heappush(heap,"B"); print heap heappop(heap) #弹出堆中最小的元素 print heap var=heappushpop(heap,"D") #返回并弹出堆中最小的元素，并且将D压入堆 print var print heap var=heapreplace(heap,"E") #返回并弹出堆中最小的元素，并且将D压入堆, print var print heap list=[1,2,3,4,5,6,7,8,9,0] heapify(list); print list print nlargest(3,list) #返回堆中最大的3个 print nsmallest(3,list) #返回堆中最小的3个 ============================================================================== 本文转自被遗忘的博客园博客，原文链接：http://www.cnblogs.com/rollenholt/archive/2011/11/26/2264225.html，如需转载请自行联系原作者
