小编Rod*_*edo的帖子

我想在cvxpy下的优化问题中添加许多约束.在matlab中我可以通过添加一行主语然后使用for循环来生成约束.我怎么能在cvxpy中做同样的工作,因为cvxpy中没有'subject'概念.有什么建议吗？

我想将以下 SDP（它只是验证约束的可行性）从 CVX (MATLAB) 转换为 CVXPY (Python)：

Ah = [1.0058, -0.0058; 1, 0];
Bh = [-1; 0];
Ch = [1.0058, -0.0058; -0.9829, 0.0056];
Dh = [-1; 1];

M = [0, 1;1, 0];
ni = size(M,1)/2;
n = size(Ah,1);
rho = 0.5;

cvx_begin sdp quiet
    variable P(n,n) semidefinite
    variable lambda(ni) nonnegative
    Mblk = M*kron(diag(lambda),eye(2));
    lambda(ni) == 1  % break homogeneity (many ways to do this...)
    [Ah Bh]'*P*[Ah Bh] - rho^2*blkdiag(P,0) + [Ch Dh]'*Mblk*[Ch Dh] <= 0
cvx_end


switch cvx_status
    case 'Solved' …

我正在尝试使用Scrapy下载我的Quora答案，但似乎无法下载我的页面。使用简单

scrapy shell 'http://it.quora.com/profile/Ferdinando-Randisi'

返回此错误

2017-10-05 22:16:52 [scrapy.utils.log] INFO: Scrapy 1.4.0 started (bot: quora)
2017-10-05 22:16:52 [scrapy.utils.log] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'quora.spiders', 'ROBOTSTXT_OBEY': True, 'DUPEFILTER_CLASS': 'scrapy.dupefilters.BaseDupeFilter', 'SPIDER_MODULES': \[quora.spiders'], 'BOT_NAME': 'quora', 'LOGSTATS_INTERVAL': 0}
....
2017-10-05 22:16:53 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2017-10-05 22:16:53 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
2017-10-05 22:16:53 [scrapy.core.engine] INFO: Spider opened
2017-10-05 22:16:54 [scrapy.downloadermiddlewares.redirect] DEBUG: Redirecting (301) to <GET https://it.quora.com/robots.txt> from <GET http://it.quora.com/robots.txt>
2017-10-05 22:16:55 [scrapy.core.engine] DEBUG: Crawled (429) <GET https://it.quora.com/robots.txt> (referer: None) …

据我所知，在Python sin(pi)和cos(pi/2)不会产生0，但我用的矩阵进行计算，我需要使用这些值。

我使用SymPy，并在第一的价值观sin(pi)和cos(pi/2)是有点讨厌。经过一些乘法后，它们开始妨碍您。有没有办法使这些值0在整个模块中等于？如何在表达式中间更改它？

我将使用此矩阵作为示例：

A = Matrix([
[(-sin(theta1)*sin(theta2)*cos(alpha2) + cos(theta1)*cos(theta2))*cos(theta3) + (-sin(theta1)*cos(alpha2)*cos(theta2) - sin(theta2)*cos(theta1))*sin(theta3)*cos(alpha3) + sin(alpha2)*sin(alpha3)*sin(theta1)*sin(theta3), -(-sin(theta1)*sin(theta2)*cos(alpha2) + cos(theta1)*cos(theta2))*sin(theta3) + (-sin(theta1)*cos(alpha2)*cos(theta2) - sin(theta2)*cos(theta1))*cos(alpha3)*cos(theta3) + sin(alpha2)*sin(alpha3)*sin(theta1)*cos(theta3), -(-sin(theta1)*cos(alpha2)*cos(theta2) - sin(theta2)*cos(theta1))*sin(alpha3) + sin(alpha2)*sin(theta1)*cos(alpha3), a3*(-sin(theta1)*sin(theta2)*cos(alpha2) + cos(theta1)*cos(theta2)) + d2*sin(alpha2)*sin(theta1) - d3*(-sin(theta1)*cos(alpha2)*cos(theta2) - sin(theta2)*cos(theta1))*sin(alpha3) + d3*sin(alpha2)*sin(theta1)*cos(alpha3)],
[(-sin(theta1)*sin(theta2) + cos(alpha2)*cos(theta1)*cos(theta2))*sin(theta3)*cos(alpha3) + (sin(theta1)*cos(theta2) + sin(theta2)*cos(alpha2)*cos(theta1))*cos(theta3) - sin(alpha2)*sin(alpha3)*sin(theta3)*cos(theta1),   (-sin(theta1)*sin(theta2) + cos(alpha2)*cos(theta1)*cos(theta2))*cos(alpha3)*cos(theta3) - (sin(theta1)*cos(theta2) + sin(theta2)*cos(alpha2)*cos(theta1))*sin(theta3) - sin(alpha2)*sin(alpha3)*cos(theta1)*cos(theta3), -(-sin(theta1)*sin(theta2) + cos(alpha2)*cos(theta1)*cos(theta2))*sin(alpha3) - sin(alpha2)*cos(alpha3)*cos(theta1),  a3*(sin(theta1)*cos(theta2) + sin(theta2)*cos(alpha2)*cos(theta1)) - d2*sin(alpha2)*cos(theta1) …

您好我已创建此程序以检查数字是否为素数.它有效,但出于某种原因说999是素数.我的错误在哪里 如果有人解释的话会很棒.谢谢!

这是我的计划:

number = raw_input('Enter a Number: ')
nnumber = int(number)
prime_range = range(2, nnumber)

for x in prime_range:

    if nnumber % x == 0:
        print 'Not a Prime Number!'
        break

    else:
        print 'Prime Number!'
        break