青青草原综合久久大伊人导航_色综合久久天天综合_日日噜噜夜夜狠狠久久丁香五月_热久久这里只有精品

Welcome to 陳俊峰's ---BeetleHeaded Man Blog !

  C++博客 :: 首頁 :: 新隨筆 :: 聯系 :: 聚合  :: 管理 ::
  58 隨筆 :: 32 文章 :: 18 評論 :: 0 Trackbacks
Subsections


10. Brief Tour of the Standard Library


10.1 Operating System Interface

The os module provides dozens of functions for interacting with the operating system:

>>> import os
>>> os.system('time 0:02')
0
>>> os.getcwd()      # Return the current working directory
'C:\\Python24'
>>> os.chdir('/server/accesslogs')

Be sure to use the "import os" style instead of "from os import *". This will keep os.open() from shadowing the builtin open() function which operates much differently.

The builtin dir() and help() functions are useful as interactive aids for working with large modules like os:

>>> import os
>>> dir(os)
<returns a list of all module functions>
>>> help(os)
<returns an extensive manual page created from the module's docstrings>

For daily file and directory management tasks, the shutil module provides a higher level interface that is easier to use:

>>> import shutil
>>> shutil.copyfile('data.db', 'archive.db')
>>> shutil.move('/build/executables', 'installdir')


10.2 File Wildcards

The glob module provides a function for making file lists from directory wildcard searches:

>>> import glob
>>> glob.glob('*.py')
['primes.py', 'random.py', 'quote.py']


10.3 Command Line Arguments

Common utility scripts often need to process command line arguments. These arguments are stored in the sys module's argv attribute as a list. For instance the following output results from running "python demo.py one two three" at the command line:

>>> import sys
>>> print sys.argv
['demo.py', 'one', 'two', 'three']

The getopt module processes sys.argv using the conventions of the Unixgetopt() function. More powerful and flexible command line processing is provided by the optparse module.


10.4 Error Output Redirection and Program Termination

The sys module also has attributes for stdin, stdout, and stderr. The latter is useful for emitting warnings and error messages to make them visible even when stdout has been redirected:

>>> sys.stderr.write('Warning, log file not found starting a new one\n')
Warning, log file not found starting a new one

The most direct way to terminate a script is to use "sys.exit()".


10.5 String Pattern Matching

The re module provides regular expression tools for advanced string processing. For complex matching and manipulation, regular expressions offer succinct, optimized solutions:

>>> 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'

When only simple capabilities are needed, string methods are preferred because they are easier to read and debug:

>>> 'tea for too'.replace('too', 'two')
'tea for two'


10.6 Mathematics

The math module gives access to the underlying C library functions for floating point math:

>>> import math
>>> math.cos(math.pi / 4.0)
0.70710678118654757
>>> math.log(1024, 2)
10.0

The random module provides tools for making random selections:

>>> import random
>>> random.choice(['apple', 'pear', 'banana'])
'apple'
>>> random.sample(xrange(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


10.7 Internet Access

There are a number of modules for accessing the internet and processing internet protocols. Two of the simplest are urllib2 for retrieving data from urls and smtplib for sending mail:

>>> import urllib2
>>> for line in urllib2.urlopen('http://tycho.usno.navy.mil/cgi-bin/timer.pl'):
...     if 'EST' in line:      # look for Eastern Standard Time
...         print line
    
<BR>Nov. 25, 09:43:32 PM EST

>>> import smtplib
>>> server = smtplib.SMTP('localhost')
>>> server.sendmail('soothsayer@example.org', 'jcaesar@example.org',
"""To: jcaesar@example.org
From: soothsayer@example.org

Beware the Ides of March.
""")
>>> server.quit()


10.8 Dates and Times

The datetime module supplies classes for manipulating dates and times in both simple and complex ways. While date and time arithmetic is supported, the focus of the implementation is on efficient member extraction for output formatting and manipulation. The module also supports objects that are time zone aware.

# 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(1964, 7, 31)
>>> age = now - birthday
>>> age.days
14368


10.9 Data Compression

Common data archiving and compression formats are directly supported by modules including: zlib, gzip, bz2, zipfile, and tarfile.

>>> 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


10.10 Performance Measurement

Some Python users develop a deep interest in knowing the relative performance of different approaches to the same problem. Python provides a measurement tool that answers those questions immediately.

For example, it may be tempting to use the tuple packing and unpacking feature instead of the traditional approach to swapping arguments. The timeit module quickly demonstrates a modest performance advantage:

>>> 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

In contrast to timeit's fine level of granularity, the profile and pstats modules provide tools for identifying time critical sections in larger blocks of code.


10.11 Quality Control

One approach for developing high quality software is to write tests for each function as it is developed and to run those tests frequently during the development process.

The doctest module provides a tool for scanning a module and validating tests embedded in a program's docstrings. Test construction is as simple as cutting-and-pasting a typical call along with its results into the docstring. This improves the documentation by providing the user with an example and it allows the doctest module to make sure the code remains true to the documentation:

def average(values):
    """Computes the arithmetic mean of a list of numbers.

    >>> print average([20, 30, 70])
    40.0
    """
    return sum(values, 0.0) / len(values)

import doctest
doctest.testmod()   # automatically validate the embedded tests

The unittest module is not as effortless as the doctest module, but it allows a more comprehensive set of tests to be maintained in a separate file:

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


10.12 Batteries Included

Python has a ``batteries included'' philosophy. This is best seen through the sophisticated and robust capabilities of its larger packages. For example:

  • The xmlrpclib and SimpleXMLRPCServer modules make implementing remote procedure calls into an almost trivial task. Despite the names, no direct knowledge or handling of XML is needed.
  • The email package is a library for managing email messages, including MIME and other RFC 2822-based message documents. Unlike smtplib and poplib which actually send and receive messages, the email package has a complete toolset for building or decoding complex message structures (including attachments) and for implementing internet encoding and header protocols.
  • The xml.dom and xml.sax packages provide robust support for parsing this popular data interchange format. Likewise, the csv module supports direct reads and writes in a common database format. Together, these modules and packages greatly simplify data interchange between python applications and other tools.
  • Internationalization is supported by a number of modules including gettext, locale, and the codecs package.
posted on 2006-04-13 19:43 Jeff-Chen 閱讀(311) 評論(0)  編輯 收藏 引用 所屬分類: Python
青青草原综合久久大伊人导航_色综合久久天天综合_日日噜噜夜夜狠狠久久丁香五月_热久久这里只有精品
  • <ins id="pjuwb"></ins>
    <blockquote id="pjuwb"><pre id="pjuwb"></pre></blockquote>
    <noscript id="pjuwb"></noscript>
          <sup id="pjuwb"><pre id="pjuwb"></pre></sup>
            <dd id="pjuwb"></dd>
            <abbr id="pjuwb"></abbr>
            国产精品入口尤物| 国产日韩精品电影| 99re热精品| 99riav久久精品riav| 国产精品久久久久久久久免费桃花| 亚洲一区二区在线免费观看| 亚洲免费视频在线观看| 精品二区视频| 91久久久亚洲精品| 欧美色道久久88综合亚洲精品| 欧美一区二区精品久久911| 久久久欧美一区二区| 亚洲伦理中文字幕| 亚洲男人av电影| 亚洲黄色成人久久久| 亚洲少妇自拍| 亚洲激情二区| 亚洲影院污污.| 亚洲精品一区在线观看| 午夜精品一区二区三区四区| 亚洲啪啪91| 欧美影院一区| 亚洲综合电影| 欧美第一黄色网| 久久天堂av综合合色| 欧美日韩一区精品| 免费观看成人| 国产精品社区| 亚洲精品久久久蜜桃| 国内精品视频在线观看| 亚洲色图自拍| 一本色道88久久加勒比精品 | 亚洲女女做受ⅹxx高潮| 亚洲激情视频网| 久久av老司机精品网站导航| 亚洲午夜av在线| 欧美3dxxxxhd| 欧美成人激情在线| 国产三级欧美三级日产三级99| 亚洲人www| 亚洲国产精品久久| 久久久精品日韩| 久久久精品国产99久久精品芒果| 欧美日韩午夜视频在线观看| 欧美激情视频给我| 亚洲第一精品福利| 久久久成人网| 久久一区二区三区四区| 国产日韩欧美夫妻视频在线观看| 日韩视频一区二区在线观看| 亚洲免费观看| 欧美成人免费在线观看| 欧美aaaaaaaa牛牛影院| 激情欧美日韩一区| 久久久久久久久久久久久久一区| 久久久精彩视频| 国内精品写真在线观看| 久久国产欧美日韩精品| 欧美一区在线视频| 国产午夜精品福利| 性色一区二区三区| 久久久综合激的五月天| 激情综合视频| 榴莲视频成人在线观看| 欧美成人精品激情在线观看| 在线欧美福利| 欧美高清你懂得| 99国产精品视频免费观看| 亚洲影院在线观看| 国产精品一区久久久| 欧美一区在线直播| 欧美成人免费播放| 一区二区三区欧美成人| 国产精品国产| 欧美一区二区三区的| 欧美jizzhd精品欧美巨大免费| 亚洲激情午夜| 国产精品成人在线| 欧美制服丝袜第一页| 亚洲国产合集| 亚洲欧美日韩精品综合在线观看| 国产日韩欧美麻豆| 麻豆成人小视频| 一区二区三区视频免费在线观看| 午夜精品理论片| 亚洲承认在线| 欧美视频手机在线| 久久久久国产精品厨房| 亚洲精品中文字幕女同| 久久久久久久久久看片| 亚洲精品一区久久久久久| 国产精品一区二区三区免费观看| 久久久亚洲高清| 中文av一区特黄| 欧美黑人国产人伦爽爽爽| 亚洲欧美日韩成人| 91久久精品视频| 国产裸体写真av一区二区| 免费在线成人av| 亚洲欧美日本国产有色| 亚洲国产精品悠悠久久琪琪| 午夜精品一区二区三区在线播放| 在线观看亚洲视频啊啊啊啊| 欧美午夜精品理论片a级大开眼界| 欧美一区二区黄| 一区二区三区你懂的| 欧美激情一二区| 久久久青草婷婷精品综合日韩| 一本到12不卡视频在线dvd| 樱桃国产成人精品视频| 国产精品毛片a∨一区二区三区|国| 久久综合国产精品| 欧美一区国产在线| 亚洲一区二区av电影| 亚洲九九九在线观看| 欧美高清在线观看| 久久夜色精品国产噜噜av| 销魂美女一区二区三区视频在线| 亚洲精品日韩在线观看| 亚洲电影在线播放| 国内在线观看一区二区三区| 国产精品女主播| 国产精品videosex极品| 欧美日韩精品欧美日韩精品 | 久久成人精品无人区| 亚洲素人在线| 一区二区欧美精品| 日韩一级欧洲| 亚洲精品在线观看免费| 亚洲黄色免费电影| 亚洲国产一区二区在线| 欧美丰满高潮xxxx喷水动漫| 久久综合亚洲社区| 久久这里只有精品视频首页| 久久久久九九视频| 久热这里只精品99re8久| 久久久噜噜噜久久人人看| 久久久噜噜噜| 免费在线日韩av| 欧美国产亚洲视频| 亚洲黄色三级| 亚洲色图综合久久| 午夜精品久久久久99热蜜桃导演| 午夜精品久久久久久久白皮肤| 亚洲欧美在线免费| 久久精品一本久久99精品| 久久午夜色播影院免费高清| 老司机亚洲精品| 欧美另类一区| 欧美午夜宅男影院在线观看| 国产精品欧美久久| 国产在线不卡| 亚洲激情另类| 亚洲一区精品视频| 久久精品视频在线| 欧美成人国产| 亚洲毛片网站| 午夜久久久久久久久久一区二区| 久久久.com| 欧美精品在线免费| 国产精品久久久久一区二区三区共 | 激情另类综合| 99re热这里只有精品视频| 亚洲一区二区三区高清不卡| 久久成人资源| 亚洲高清免费视频| 亚洲一区欧美| 快射av在线播放一区| 欧美色123| 一区免费视频| 亚洲欧美日韩国产一区二区三区 | 亚洲欧美日本另类| 女人色偷偷aa久久天堂| 一区二区精品| 久久天天综合| 国产精品免费久久久久久| 精品成人久久| 亚洲欧美日韩精品| 亚洲承认在线| 午夜精品美女久久久久av福利| 麻豆91精品| 国产手机视频一区二区| 一区二区三区福利| 浪潮色综合久久天堂| 亚洲一区国产精品| 欧美刺激性大交免费视频| 国产欧美一区二区三区另类精品 | 国产欧美精品日韩精品| 日韩性生活视频| 老妇喷水一区二区三区| 亚洲伊人伊色伊影伊综合网 | 亚洲欧美日韩一区二区三区在线观看| 欧美a级一区二区| 国外成人在线| 欧美一区二区三区四区在线观看 | 久久香蕉国产线看观看网| 国产欧美韩国高清| 亚洲一区二区免费看| 亚洲欧洲一级| 欧美成人午夜激情视频|