Python Tutorial 笔记4

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Standard Library
　　

Library Name	Usage	Sample
os	提供一些类似于Shell的操作	>>> import os >>> os.system('time 0:02') 0 >>> os.getcwd()      # Return the current working directory 'C:\\Python30' >>> os.chdir('/server/accesslogs')
shutil	文件和目录管理	>>> import shutil >>> shutil.copyfile('data.db', 'archive.db') >>> shutil.move('/build/executables', 'installdir')
glob	支持通配符的文件搜索	>>> import glob >>> glob.glob('*.py') ['primes.py', 'random.py', 'quote.py']
sys.argv 　　getopt 　　optparse	输入参数
re	正则表达式	>>> import re >>> re.findall(r'\bf[a-z]*', 'which foot or hand fell fastest') ['foot', 'fell', 'fastest'] >>> re.sub(r'(\b[a-z]+) \1', r'\1', 'cat in the the hat') 'cat in the hat'
random	随机函数	>>> import random >>> random.choice(['apple', 'pear', 'banana']) 'apple' >>> random.sample(range(100), 10)   # sampling without replacement [30, 83, 16, 4, 8, 81, 41, 50, 18, 33] >>> random.random()    # random float 0.17970987693706186 >>> random.randrange(6)    # random integer chosen from range(6) 4
datetime	日期时间	# dates are easily constructed and formatted >>> from datetime import date >>> now = date.today() >>> now datetime.date(2003, 12, 2) >>> now.strftime("%m-%d-%y. %d %b %Y is a %A on the %d day of %B.") '12-02-03. 02 Dec 2003 is a Tuesday on the 02 day of December.' # dates support calendar arithmetic >>> birthday = date(2005, 3, 6) >>> age = now - birthday >>> age.days 14368

　　

zlib 　　gzip 　　bz2          　　tarfile 　　zipfile	压缩解压缩	>>> import zlib >>> s = 'witch which has which witches wrist watch' >>> len(s) 41 >>> t = zlib.compress(s) >>> len(t) 37 >>> zlib.decompress(t) 'witch which has which witches wrist watch' >>> zlib.crc32(s) 226805979
timeit	测量时间	>>> from timeit import Timer >>> Timer('t=a; a=b; b=t', 'a=1; b=2').timeit() 0.57535828626024577 >>> Timer('a,b = b,a', 'a=1; b=2').timeit() 0.54962537085770791
unittest	单元测试	import unittest class TestStatisticalFunctions(unittest.TestCase): def test_average(self): self.assertEqual(average([20, 30, 70]), 40.0) self.assertEqual(round(average([1, 5, 7]), 1), 4.3) self.assertRaises(ZeroDivisionError, average, []) self.assertRaises(TypeError, average, 20, 30, 70) unittest.main() # Calling from the command line invokes all tests
Template	模板替换	>>> t = Template('${village} folk send $$10 to $cause') >>> t.safe_substitute(village='nottingham', cause='the ditch fund') 'village folk send $10 to the ditch fund'
MultiThread	多线程	import threading, zipfile class AsyncZip(threading.Thread): def __init__(self, infile, outfile): threading.Thread.__init__(self) self.infile = infile self.outfile = outfile def run(self): f = zipfile.ZipFile(self.outfile, 'w', zipfile.ZIP_DEFLATED) f.write(self.infile) f.close() print('Finished background zip of:', self.infile) background = AsyncZip('mydata.txt', 'myarchive.zip') background.start() print('The main program continues to run in foreground.') background.join()    # Wait for the background task to finish print('Main program waited until background was done.')
Logging	日志	import logging logging.debug('Debugging information') logging.info('Informational message') logging.warning('Warning:config file %s not found', 'server.conf') logging.error('Error occurred') logging.critical('Critical error -- shutting down') WARNING:root:Warning:config file server.conf not found ERROR:root:Error occurred CRITICAL:root:Critical error -- shutting down
Weak References	弱指针	import gc import weakref class Value: def __init__(self, value=0): self.value = value def __repr__(self): return str(self.value) if __name__ == '__main__': d = {} v = Value(10) d['myvalue'] = v del v gc.collect() print(d['myvalue']) e = weakref.WeakValueDictionary() v = Value(11) e['myvalue'] = v del v gc.collect() print(e['myvalue'])
array 　　deque 　　bisect 　　heapq	容器
decimal	精确计算	>>> Decimal('1.00') % Decimal('.10') Decimal("0.00") >>> 1.00 % 0.10 0.09999999999999995 >>> sum([Decimal('0.1')]*10) == Decimal('1.0') True >>> sum([0.1]*10) == 1.0 False >>> getcontext().prec = 36 >>> Decimal(1) / Decimal(7) Decimal("0.142857142857142857142857142857142857")