Question

我正在尝试让我了解每次计算hori_dist时的增量增加。相反，它只是向我显示最终结果加在一起。由于我的范围是5，如何获取5个值？

通过Google搜索视频，在线搜索，并尝试了多种方式

#include <boost/graph/adjacency_list.hpp>
#include <iostream>

struct PropertyObj {
    std::string something;
};

template <class Graph, class T = PropertyObj>
class Wrapper {
  public:
    using vertex_descriptor = typename Graph::vertex_descriptor;
    T& get_property_obj(vertex_descriptor v) {
        if (!descriptor_looks_valid(v)) 
            throw std::range_error("get_property_obj");
        return g[v];
    }
    Wrapper(Graph& g) : g(g){}
  private:
    bool descriptor_looks_valid(vertex_descriptor v) const {
        if constexpr(std::is_integral_v<vertex_descriptor>) {
            return v>=0 && v < num_vertices(g);
        } else {
            auto vds = vertices(g);
            return std::count(vds.first, vds.second, v);
        }
    }

    Graph& g;
};

template <typename vertexS> void doTest() {
    using Graph = boost::adjacency_list<
        boost::vecS,
        vertexS,
        boost::directedS,
        PropertyObj>;

    Graph g;
    auto v1 = add_vertex({"one"}, g);
    auto v2 = add_vertex({"two"}, g);
    auto v3 = add_vertex({"three"}, g);
    auto v4 = add_vertex({"four"}, g);
    auto v5 = add_vertex({"five"}, g);

    boost::ignore_unused_variable_warning(v1);
    boost::ignore_unused_variable_warning(v2);
    boost::ignore_unused_variable_warning(v3);
    boost::ignore_unused_variable_warning(v4);
    boost::ignore_unused_variable_warning(v5);

    Wrapper w = g;
    std::cout << w.get_property_obj(v3).something << std::endl;

    // but this is confounding, and only accidentally "works" for vecS:
    remove_vertex(v1, g);
    std::cout << w.get_property_obj(v3).something << std::endl;

    try {
        // this looks "valid" with vecS, but should throw for listS
        //
        // of course, like with v3 the descriptor was already invalidated both cases
        std::cout << w.get_property_obj(v1).something << std::endl;
    } catch(std::range_error const& re) {
        std::cout << "(range_error caught: " << re.what() << "\n";
    }
}

int main() {
    std::cout << "Testing with vecS:\n";
    doTest<boost::vecS>();

    std::cout << "\nTesting with listS:\n";
    doTest<boost::listS>();

    std::cout << "\nTesting with setS:\n";
    doTest<boost::setS>();
}

Answer 1

要定义范围，许多语言都使用花括号 {} 。但是，Python使用缩进。

因此，如果您希望某件东西被打印5次，则可以将其包含在for循环中。可能会对您有帮助。

Vx0 = 18
Vy0 = 18
V = 18
Theta = 45
y0 = 1.8    
x0 = 0
p = 1.2 #given density
C = 0.3 #Drag coefficient
dt = 0.2 #Time increment

def x_direction (x0, Vx0, dt):
    """Calculate the distance moved in x axis"""
    new_dist = 0
    for hori_dist in range(5):
        hori_dist = x0 + Vx0*dt
        new_dist = new_dist + hori_dist
        print ("[LOOP] Distance being moved is", hori_dist) #The extra print
        print ("[LOOP] New distance is", new_dist) #Another extra print
    return new_dist

new_dist = x_direction(x0, Vx0, dt)
print ("Distanced moved in x direction is :", new_dist)

Answer 2

只需将print语句放入循环中，就像这样

hori_dist = x0 + Vx0*dt print (hori_dist)

此外，您不能像在这里x_direction(x0, Vx0, dt)那样调用函数。您应该传递值而不是变量x_direction(0, 18, 0.2)

我如何从1个循环中获得多个输出？

2 个答案: