方法一:
>>> help('modules')
Please wait a moment while I gather a list of all available modules...
....
Enter any module name to get more help. Or, type "modules spam" to search
for modules whose descriptions contain the word "spam".
方法二:
>>> import sys >>> sys.modules
在php中可以知道 ip2long 函数将ip转为整型，long2ip将整型转为ip，从而方便计算。
ip分为四段，将第一段*256^3，第二段*256^2，第三段*256^1，第四段*256^0，最后相加，这样就计算出了一个唯一的值。如果都是最大值，算出来的值是
>>> 255*256*256*256 + 255*256*256 + 255*256 + 255
4294967295
我们可以发现mysql中int型的取值范围是4个字节，十进制为
0 到 4294967295
所以所有的ipv4地址用mysql的int恰好可以完整记录
python中互相转换的方法如下
import socket
import struct
def ip2long(ipstr):
return struct.unpack("!I", socket.inet_aton(ipstr))[0]
def long2ip(ip):
return socket.inet_ntoa(struct.pack("!I", ip))
http://hily.me/blog/2009/03/python-ip2long-long2ip/
以下脚本是读取以空格分开的字段(weight.txt)变成以逗号分隔(weight.csv)
#!/usr/bin/env python
#-*- coding:utf-8 -*-
# author jpuyy.com
import csv
reader = csv.reader(open('weight.txt', 'rb'), delimiter=' ', quoting=csv.QUOTE_NONE)
writer = csv.writer(open('weight.csv', 'wb'))
for row in reader:
writer.writerow(row)
解决 csv 用 excel 打开乱码问题
import codecs file_obj = open(csv_name, "wb+") file_obj.write(codecs.BOM_UTF8) f = csv.writer(file_obj)
Django为流行的python web开发框架
安装python的包管理器，easy_install
# apt-get install python-setuptools
可以使用下面的命令检查是否安装成功
# easy_install --version
显示版本信息则安装成功
接下来使用easy_install安装Django
# easy_install django
使用如下命令查看django是否安装成功
# python Python 2.7.3 (default, Aug 1 2012, 05:14:39) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import django >>> django.VERSION (1, 4, 3, 'final', 0)
出现版本信息，则表示安装成功。
http://jpuyy.com/2012/12/python-simple-programs-a.html
http://jpuyy.com/2013/01/python-simple-programs-b.html
例.20 素数筛选，生成器–Prime numbers sieve w/fancy generators
生成从2到1000以内的素数
import itertools
def iter_primes():
# an iterator of all numbers between 2 and +infinity
numbers = itertools.count(2)
# generate primes forever
while True:
# get the first number from the iterator (always a prime)
prime = numbers.next()
yield prime
# this code iteratively builds up a chain of
# filters...slightly tricky, but ponder it a bit
numbers = itertools.ifilter(prime.__rmod__, numbers)
for p in iter_primes():
if p > 1000:
break
print p
例21.xml/html解析–XML/HTML parsing
dinner_recipe = '''<html><body><table>
<tr><th>amt</th><th>unit</th><th>item</th></tr>
<tr><td>24</td><td>slices</td><td>baguette</td></tr>
<tr><td>2+</td><td>tbsp</td><td>olive oil</td></tr>
<tr><td>1</td><td>cup</td><td>tomatoes</td></tr>
<tr><td>1</td><td>jar</td><td>pesto</td></tr>
</table></body></html>'''
# In Python 2.5 or from http://effbot.org/zone/element-index.htm
import xml.etree.ElementTree as etree
tree = etree.fromstring(dinner_recipe)
# For invalid HTML use http://effbot.org/zone/element-soup.htm
# import ElementSoup, StringIO
# tree = ElementSoup.parse(StringIO.StringIO(dinner_recipe))
pantry = set(['olive oil', 'pesto'])
for ingredient in tree.getiterator('tr'):
amt, unit, item = ingredient
if item.tag == "td" and item.text not in pantry:
print "%s: %s %s" % (item.text, amt.text, unit.text)
例28. 8皇后问题(自定义例外)8-Queens Problem (define your own exceptions)
BOARD_SIZE = 8
class BailOut(Exception):
pass
def validate(queens):
left = right = col = queens[-1]
for r in reversed(queens[:-1]):
left, right = left-1, right+1
if r in (left, col, right):
raise BailOut
def add_queen(queens):
for i in range(BOARD_SIZE):
test_queens = queens + [i]
try:
validate(test_queens)
if len(test_queens) == BOARD_SIZE:
return test_queens
else:
return add_queen(test_queens)
except BailOut:
pass
raise BailOut
queens = add_queen([])
print queens
print "\n".join(". "*q + "Q " + ". "*(BOARD_SIZE-q-1) for q in queens)
import random
guesses_made = 0
name = raw_input('Hello! What is your name?\n')
number = random.randint(1, 20)
print 'Well, {0}, I am thinking of a number between 1 and 20.'.format(name)
while guesses_made < 6:
guess = int(raw_input('Take a guess: '))
guesses_made += 1
if guess < number:
print 'Your guess is too low.'
if guess > number:
print 'Your guess is too high.'
if guess == number:
break
if guess == number:
print 'Good job, {0}! You guessed my number in {1} guesses!'.format(name, guesses_made)
else:
print 'Nope. The number I was thinking of was {0}'.format(number)
接着上一个http://jpuyy.com/2012/12/python-simple-programs-a.html
例11.三引号，while循环–Triple-quoted strings, while loop
REFRAIN = '''
%d bottles of beer on the wall,
%d bottles of beer,
take one down, pass it around,
%d bottles of beer on the wall!
'''
bottles_of_beer = 99
while bottles_of_beer > 1:
print REFRAIN % (bottles_of_beer, bottles_of_beer,
bottles_of_beer - 1)
bottles_of_beer -= 1
例12.python中的类–Classes
class BankAccount(object):
def __init__(self, initial_balance=0):
self.balance = initial_balance
def deposit(self, amount):
self.balance += amount
def withdraw(self, amount):
self.balance -= amount
def overdrawn(self):
return self.balance < 0
my_account = BankAccount(15)
my_account.withdraw(5)
print my_account.balance
执行结果是10
例13.使用unittest模块进行单元测试–Unit test with unittest
import unittest
def median(pool):
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[(size - 1) / 2]
else:
return (copy[size/2 - 1] + copy[size/2]) / 2
class TestMedian(unittest.TestCase):
def testMedian(self):
self.failUnlessEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7)
if __name__ == '__main__':
unittest.main()
执行过程：将中间值计算出来与7比较，如果相等，则通过测试。
例14.基于Doctest的测试–Doctest-based testing
def median(pool):
'''Statistical median to demonstrate doctest.
>>> median([2, 9, 9, 7, 9, 2, 4, 5, 8])
7
'''
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[(size - 1) / 2]
else:
return (copy[size/2 - 1] + copy[size/2]) / 2
if __name__ == '__main__':
import doctest
doctest.testmod()
执行结果：没有输出任何东西，说明中间值是7
例15.使用itertools模块
from itertools import groupby
lines = '''
This is the
first paragraph.
This is the second.
'''.splitlines()
# Use itertools.groupby and bool to return groups of
# consecutive lines that either have content or don't.
for has_chars, frags in groupby(lines, bool):
if has_chars:
print ' '.join(frags)
# PRINTS:
# This is the first paragraph.
# This is the second.
例16.csv模块，元组拆分，内置函数cmp() — csv module, tuple unpacking, cmp() built-in
import csv
# write stocks data as comma-separated values
writer = csv.writer(open('stocks.csv', 'wb', buffering=0))
writer.writerows([
('GOOG', 'Google, Inc.', 505.24, 0.47, 0.09),
('YHOO', 'Yahoo! Inc.', 27.38, 0.33, 1.22),
('CNET', 'CNET Networks, Inc.', 8.62, -0.13, -1.49)
])
# read stocks data, print status messages
stocks = csv.reader(open('stocks.csv', 'rb'))
status_labels = {-1: 'down', 0: 'unchanged', 1: 'up'}
for ticker, name, price, change, pct in stocks:
status = status_labels[cmp(float(change), 0.0)]
print '%s is %s (%s%%)' % (name, status, pct)
例18. 八皇后问题，递归–8-Queens Problem (recursion)
BOARD_SIZE = 8
def under_attack(col, queens):
left = right = col
for r, c in reversed(queens):
left, right = left - 1, right + 1
if c in (left, col, right):
return True
return False
def solve(n):
if n == 0:
return [[]]
smaller_solutions = solve(n - 1)
return [solution+[(n,i+1)]
for i in xrange(BOARD_SIZE)
for solution in smaller_solutions
if not under_attack(i+1, solution)]
for answer in solve(BOARD_SIZE):
print answer