python 随笔

>>>squared = [x**2 for x in range(4)]

>>>for i in squared:

... 　　　　print i

0 

1

4

9

>>>sqdEvens=[x**2 for x in range(8) if not x%2]

try:

filename=raw_input('Enter file name:')

fobj=open(filename,'r')

for eachLine in fobj:

print eachLine,

fobj.close()

except IOError, e:

print 'file open error:',e

form string import Template

s=Template('There are ${howmany} ${lang} Quotation Symbols')

print s.substitute(lang='Python', howmany=3) There are 3 Python Quotation Sysbols

string.capitalize() 把字符串的第一个字符大写

string.center(width)

string.count(str,beg=0,end=len(string))

string.decode(encoding='UTF-8',errors='strict')

string.encode(encoding='UTF-8',error='strict')

dict['name']='venus'

dict['port']=6969

dict['arch']='sunos5'

print 'host %(name)s is running on port  %(port)d '%dict

host venus is running on port 6969

列表

append() 列表末尾+

pop() 列表末尾-

extend() 列表末尾+数据项集合

 try:

except []:

finally:

 推导列表

a=[b(c) for c in d]

import os.path

TEMPLATE_DIRS = (
    os.path.join(os.path.dirname(__file__), 'templates').replace('\','/'),
)

  `` os.path.dirname(__file__)`` 将会获取自身所在的文件

一旦你觉得你的模型可能有问题，运行 python manage.py validate 。 它可以帮助你捕获一些常见的模型定义错误

python manage.py syncdb

syncdb 命令是同步你的模型到数据库的一个简单方法

Publisher.objects.filter(name='Apress')

Publisher.objects.filter(name__contains="press")
在 name 和 contains 之间有双下划线。和Python一样，Django也使用双下划线来表明会进行一些魔术般的操作。这里，contains部分会被Django翻译成LIKE语句：

上面的例子中`` filter()`` 函数返回一个记录集，这个记录集是一个列表。 相对列表来说，有些时候我们更需要获取单个的对象， `` get()`` 方法就是在此时使用的：

Publisher.objects.order_by("name")

Publisher.objects.order_by("-name")

class Book(models.Model):
    title = models.CharField(max_length=100)
    authors = models.ManyToManyField(Author)
    publisher = models.ForeignKey(Publisher)
    publication_date = models.DateField(**blank=True, null=True** )

num_pages = models.IntegerField(blank=True, null=True)设置可选字段

from django.db import connection

def user_contacts(request):
    user = request.GET['username']
    sql = "SELECT * FROM user_contacts WHERE username = %s"
    cursor = connection.cursor()
    cursor.execute(sql, [user])
    # ... do something with the results

def my_custom_sql(self):
    from django.db import connection
    cursor = connection.cursor()
    cursor.execute("SELECT foo FROM bar WHERE baz = %s", [self.baz])
    row = cursor.fetchone()
    return row