Python标准库简介

os模块提供了不少与操作系统相关联的函数

>>> import os
>>> os.getcwd()      # 返回当前的工作目录
'C:\\Python34'
>>> os.chdir('/server/accesslogs')   # 修改当前的工作目录
>>> os.system('mkdir today')   # 执行系统命令 mkdir 
0

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

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

glob模块提供了一个函数用于从目录通配符搜索中生成文件列表

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

通用工具脚本经常调用命令行参数。这些命令行参数以链表形式存储于 sys 模块的 argv 变量

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

re模块为高级字符串处理提供了正则表达式工具。对于复杂的匹配和处理，正则表达式提供了简洁、优化的解决方案

>>> 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'

math模块为浮点运算提供了对底层C函数库的访问

>>> import math
>>> math.cos(math.pi / 4)
0.70710678118654757
>>> math.log(1024, 2)
10.0

>>> 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模块为日期和时间处理同时提供了简单和复杂的方法

>>> # 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