python cookbook(1)（每章代码记录，坚持......）

import collectionsimport heapqfrom _collections import defaultdictfrom collections import OrderedDictimport jsonp = (4,5)x, y = pprint(x, y)data = ['ACME', 50, 91.1, (2012,12,21)]name, shares, price, date = dataprint(name, shares, price, date)#p = (4, 5)#x, y, z = ps = 'Hello'a, b, c, d, e = sprint(a, b, c, d, e)_, shares, price, _ = dataprint(shares, price)print("*************************************************")record = ('Dave', '[e-mail]', '773-555-1212', '847-555-1212')name, email, *phone_numbers = recordprint(name)print(email)print(phone_numbers)print("*************************************************")name, *phone_numbers, email = recordprint(name)print(phone_numbers)print(email)print("*************************************************")line = 'nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false'uname, *fields, homedir, sh = line.split(':')print(uname)print(fields)print(homedir)print(sh)print("*************************************************")record = ('ACME', 50, 123.45, (12,18,2012))name, *_, (*_, year) = recordprint(name, year)print("*************************************************")q = collections.deque(maxlen=3)q.append(1)q.append(2)q.append(3)print(q)q.append(4)print(q)q = collections.deque()q.append(1)q.append(2)q.append(3)print(q)q.appendleft(4)print(q)print(q.pop())print(q)print(q.popleft())print(q)print("*************************************************")nums = [1,8,2,23,7,-4,18,23,42,37,2]print(heapq.nlargest(3, nums))print(heapq.nsmallest(3, nums))portfolio = [    {'name':'IBM', 'shares':100, 'price':91.1},    {'name':'AAPL', 'shares':50, 'price':543.22},    {'name':'FB', 'shares':200, 'price':21.09},    {'name':'HPQ', 'shares':35, 'price':31.75},    {'name':'YHOO', 'shares':45, 'price':16.35},    {'name':'ACME', 'shares':75, 'price':115.65},]cheap = heapq.nsmallest(3, portfolio, key=lambda s : s['price'])expensive = heapq.nlargest(3, portfolio, key=lambda s : s['price'])print(cheap)print(expensive)print("*************************************************")nums = [1,8,2,23,7,-4,18,23,42,37,2]heap = list(nums)print(heap)heapq.heapify(heap)print(heap)print(heapq.heappop(heap))print(heapq.heappop(heap))print(heapq.heappop(heap))print("*************************************************")class PriorityQueue:    def __init__(self):        self._queue = []        self._index = 0    def push(self, item, priority):        heapq.heappush(self._queue, (-priority, self._index, item))        self._index += 1    def pop(self):        return heapq.heappop(self._queue)[-1]class Item:    def __init__(self, name):        self.name = name    def __repr__(self):        return 'Item({!r})'.format(self.name)q = PriorityQueue()q.push(Item('foo'), 1)q.push(Item('bar'), 5)q.push(Item('spam'), 4)q.push(Item('grok'), 1)print(q)print(q.pop())print(q.pop())print(q.pop())print(q.pop())print("*************************************************")#a = Item('foo')#b = Item('bar')#print(a < b)a = (1, Item('foo'))b = (5, Item('bar'))print(a < b)c = (1, Item('grok'))#print(a < c)d = {    'a' : [1,2,3],    'b' : [4,5]}e = {    'a' : {1,2,3},    'b' : {4,5}}d = defaultdict(list)d['a'].append(1)d['a'].append(2)d['b'].append(4)print(d)d = defaultdict(set)d['a'].add(1)d['a'].add(2)d['b'].add(4)print(d)d = {}d.setdefault('a', []).append(1)d.setdefault('a', []).append(2)d.setdefault('b', []).append(3)print(d)print("*************************************************")d = OrderedDict()d['foo'] = 1d['bar'] = 2d['spam'] = 3d['grok'] = 4for key in d:    print(key, d[key])print(json.dumps(d))print("*************************************************")prices = {    'ACME':45.23,    'AAPL':612.78,    'IBM':205.55,    'HPQ':37.20,    'FB':10.75}min_price = min(zip(prices.values(), prices.keys()))print(min_price)max_price = max(zip(prices.values(), prices.keys()))print(max_price)prices_sorted = sorted(zip(prices.values(), prices.keys()))print(prices)print(min(prices.values()), max(prices.values()))#print(prices[min(prices, key=lambda k : prices[k])])#print(prices[max(prices, key=lambda k : prices(k))])prices = {'AAA':45.23, 'ZZZ':45.23}print(min(zip(prices.values(), prices.keys())))print(max(zip(prices.values(), prices.keys())))print("*************************************************")a = {    'x':1,    'y':2,    'z':3}b = {    'w':10,    'x':11,    'y':2}print(a.keys() & b.keys())print(a.keys() - b.keys())print(a.items() & b.items())c = {key:a[key] for key in a.keys()}print(c)c = {key:a[key] for key in a.keys() - {'z', 'w'}}print(c)print("*************************************************")'''def dedupe(items):    seen = set()    for item in items:        if item not in seen:            yield item            seen.add(item)a = [1,5,2,1,9,1,5,10]print(list(dedupe(a)))'''def dedupe(items, key=None):    seen =  set()    for item in items:        val = item if key is None else key(item)        if val not in seen:            yield item            seen.add(val)a = [{'x':1, 'y':2}, {'x':1, 'y':3}, {'x':1, 'y':2}, {'x':2, 'y':4}]print(list(dedupe(a, key=lambda d : (d['x'], d['y']))))print(list(dedupe(a, key=lambda d : d['x'])))print("*************************************************")items = [0,1,2,3,4,5,6]a = slice(2,4)print(a)print(items[a])a = slice(1,6,2)print(items[a])s = 'HelloWorld'print(a.indices(len(s)))for i in range(*a.indices(len(s))):    print(i, s[i])print("*************************************************")words = ['look', 'into', 'my', 'eyes', 'look', 'into', 'my', 'eyes','the', 'eyes', 'the', 'eyes', 'the', 'eyes', 'not', 'around', 'the','eyes', "don't", 'look', 'around', 'the', 'eyes', 'look', 'into','my', 'eyes', "you're", 'under']from collections import Counterword_counts = Counter(words)top_three = word_counts.most_common(4)print(top_three)print(word_counts['not'])print(word_counts['eyes'])print("*************************************************")rows = [    {'fname': 'Brian', 'lname': 'Jones', 'uid': 1003},    {'fname': 'David', 'lname': 'Beazley', 'uid': 1002},    {'fname': 'John', 'lname': 'Cleese', 'uid': 1001},    {'fname': 'Big', 'lname': 'Jones', 'uid': 1004}]from operator import itemgetterrows_by_fname = sorted(rows, key=itemgetter('fname'))rows_by_uid = sorted(rows, key=itemgetter('uid'))print(rows_by_fname)print(rows_by_uid)rows_by_lfname = sorted(rows, key=itemgetter('lname', 'fname'))print(rows_by_lfname)print(min(rows, key=itemgetter('uid')))print(max(rows, key=itemgetter('uid')))print("*************************************************")rows = [    {'address': '5412 N CLARK', 'date': '07/01/2012'},    {'address': '5148 N CLARK', 'date': '07/04/2012'},    {'address': '5800 E 58TH', 'date': '07/02/2012'},    {'address': '2122 N CLARK', 'date': '07/03/2012'},    {'address': '5645 N RAVENSWOOD', 'date': '07/02/2012'},    {'address': '1060 W ADDISON', 'date': '07/02/2012'},    {'address': '4801 N BROADWAY', 'date': '07/01/2012'},    {'address': '1039 W GRANVILLE', 'date': '07/04/2012'},]from itertools import groupbyrows.sort(key=itemgetter('date'))for date, items in groupby(rows, key=itemgetter('date')):    print(date)    for i in items:        print('    ', i)print("*************************************************")mylist = [1,4,-5,10,-7,2,3,-1]print([n for n in mylist if n >0])  values = ['1', '2', '-3', '-', '4', 'N/A', '5']def is_int(val):    try:        x = int(val)        return True    except ValueError:        return Falseivals = list(filter(is_int, values))print(ivals)import mathprint([math.sqrt(n) for n in mylist if n > 0 ]) clip_neg = [n if n > 0 else 0 for n in mylist]print(clip_neg)clip_pos = [n if n < 0 else 0 for n in mylist]print(clip_pos)print("*************************************************")addresses = [    '5412 N CLARK',    '5148 N CLARK',    '5800 E 58TH',    '2122 N CLARK'    '5645 N RAVENSWOOD',    '1060 W ADDISON',    '4801 N BROADWAY',    '1039 W GRANVILLE',]counts = [0,3,10,4,1,7,6,1]from itertools import compressmore5 = [n > 5 for n in counts]print(list(compress(addresses, more5)))print("*************************************************")prices = {    'ACME': 45.23,    'AAPL': 612.78,    'IBM': 205.55,    'HPQ': 37.20,    'FB': 10.75}       p1 = {key:value for key, value in prices.items()}tech_names = ['AAPL', 'IBM', 'HPQ', 'MSFT']p2 = {key:value for key, value in prices.items() if key in tech_names}print(p2)p3 = dict((key, value) for key, value in prices.items())tech_names = {'AAPL', 'IBM', 'HPQ', 'MSFT'}print(p3)p4 = { key:prices[key] for key in prices.keys() & tech_names }print(p4)from collections import namedtupleprint("*************************************************")Subscriber = namedtuple('Subscriber', ('addr', 'joined'))sub = Subscriber('[e-mail]', '2012-10-19')print(sub)print(sub.addr, sub.joined)addr, joined = sub print(addr, joined)Stock = namedtuple('Stock', ['name', 'shares', 'price'])s = Stock('ACME', shares=100, price=123.45)print(s)#s.shares = 75s = s._replace(shares=75)print(s)Stock = namedtuple('Stock', ['name', 'shares', 'price', 'date', 'time'])stock_prototype = Stock('', 0, 0.0, None, None)def dick_to_stock(s):    return stock_prototype._replace(**s)a = {'name':'ACME', 'shares':100, 'price':123.45}print(dick_to_stock(a))print("*************************************************")nums = [1,2,3,4,5]s = sum(x * x for x in nums)print(s)s = ('ACME', 50, 123.45)print(','.join(str(x) for x in s))portfolio = [    {'name':'GOOG', 'shares': 50},    {'name':'YHOO', 'shares': 75},    {'name':'AOL', 'shares': 20},    {'name':'SCOX', 'shares': 65}]min_shares = min(s['shares'] for s in portfolio)print(min_shares)print("*************************************************")a = {'x':1, 'z':3}b = {'y':2, 'z':4}from collections import ChainMapc = ChainMap(a, b)print(c)print(c['x'], c['y'], c['z'])print(c.keys())print(list(c.keys()))print(list(c.values()))merged = dict(b)merged.update(a)print(merged)print(merged['x'])print(merged['y'])print(merged['z'])a['x'] = 13print(merged['x'])merged.update(a)print(merged['x'])merged = ChainMap(a, b)print(merged['x'])a['x'] = 42print(merged['x'])