检查我的以下代码; 它是在python中实现的sigma_2函数(使用原始筛选)的一部分,它是除数函数之一http://mathworld.wolfram.com/DivisorFunction.html
from time import time
from itertools import count
import numpy
def sig2(N, nump=False):
init = time()
#initialize array with value=1 since every positive integer is divisible by 1
if nump:
print 'using numpy'
nums = numpy.ones((N,), dtype=numpy.int64)
else:
nums = [1 for i in xrange(1, N)]
#for each number n < N, add n*n to n's multiples
for n in xrange(2, N):
nn = n*n
for i in count(1):
if n*i >= N: break
nums[n*i-1] += nn …我不得不写一些覆盖的类__getattribute__.基本上我的类是一个容器,它将每个用户添加的属性保存到self._meta字典中.
class Container(object):
def __init__(self, **kwargs):
super(Container, self).__setattr__('_meta', OrderedDict())
#self._meta = OrderedDict()
super(Container, self).__setattr__('_hasattr', lambda key : key in self._meta)
for attr, value in kwargs.iteritems():
self._meta[attr] = value
def __getattribute__(self, key):
try:
return super(Container, self).__getattribute__(key)
except:
if key in self._meta : return self._meta[key]
else:
raise AttributeError, key
def __setattr__(self, key, value):
self._meta[key] = value
#usage:
>>> a = Container()
>>> a
<__main__.Container object at 0x0000000002B2DA58>
>>> a.abc = 1 #set an attribute
>>> a._meta
OrderedDict([('abc', 1)]) …我正在使用python动态创建一个jQuery函数:
jQuery = ("$('%(other_id)').click(function() { "
" if ($(this).is(':checked')) { "
" $('%(text_id)').show() "
" } "
" else {"
" $('%(text_id)').hide()"
" }"
" });")
我要插入可变因素成other_id和text_id.我看到该$符号用于字符串模板(不知道它做了什么)所以我用double- $s($$)来逃避它们
jQuery = ("$$('%(other_id)').click(function() { "
" if ($$(this).is(':checked')) { "
" $$('%(text_id)').show() "
" } "
" else {"
" $$('%(text_id)').hide()"
" }"
" });")
但是我还是不能格式化这个:
>>> choice_id = 'foo'
>>> text_choice_id = 'bar'
>>> jQuery = ("$$('%(other_id)').click(function() { "
" if ($$(this).is(':checked')) …在python中,对于iterables,可以构造许多单行迭代命令.
对于某些此类迭代,需要if语句.
有时if语句和for语句的顺序很重要.假设我想找到0到10之间的奇数之和:
>>> sum(i if not i%2==0 for i in range(10))
SyntaxError: invalid syntax
>>> sum(i for i in range(10) if not i%2==0)
25
这些单行本身不是很理解,但我真的不明白为什么if语句有来后的for语句.使用前一个不是更合适的常识i if not i%2==0 for i in range(10)吗？