使用具有给定值的python打印三角形金字塔

Question

I have printed a triangle pyramid like this:

     * 
    * * 
   * * * 
  * * * * 
 * * * * * 

My code is:

for i in range(1,6):
    for j in range(6-i):
        print(" ", end="")
    for j in range(i):
        print("*", end=" ")
    print()

I want to print a triangle like this star pyramid: If I input 1: print first image then if I input 2 print second one. I want to know the actual logic.

Answer 1

Considering the scalability of code, I have define two paramters, size and layer :

• size is height of triangle also star numbers of bottom
• layer is layer of triangles you want to pile up

Here are some keypoints:

1. str.center is very helpful here. If we know the width , it can automaticly put it in the middle of it. so with help of center , if we calculate the star number and margine between them. we can build a triangle easily.

2. implement the function to produce a single triangle: first print top , then body , last bottom .

3. compose single triangles together in same layer, layer 0 has 1 triangle, layer 1 has 2 triangles... we can just calculate the number of triangles in current layer and concat them by corresponding string, and then use total_width to put them in center again.

Here is my solution:

from functools import reduce

def generate_triangle(size, width):
    res = []
    # print top
    res.append('*'.center(width))

    # print body
    margin = 1
    for i in range(size - 2):
        res.append(('*' + ' ' * margin + '*').center(width))
        margin += 2

    # print bottom
    res.append(' '.join('*' * size).center(width))
    return res

def generate_triangles(size, layer):
    width = size * 2 - 1
    total_width = layer * (width + 1) - 1
    res = []
    for i in range(layer):
        res += reduce(lambda x, y: x + [' '.join(y for _ in range(i + 1)).center(total_width)],
                      generate_triangle(size, width), [])
    return res

test code:

def triangle_test():
    def print_matrix(matrix):
        for row in matrix:
            print(row)
        print()

    print_matrix(generate_triangles(6, 1))
    print_matrix(generate_triangles(5, 2))
    print_matrix(generate_triangles(4, 4))

output:

     *     
    * *    
   *   *   
  *     *  
 *       * 
* * * * * *

         *         
        * *        
       *   *       
      *     *      
     * * * * *     
    *         *    
   * *       * *   
  *   *     *   *  
 *     *   *     * 
* * * * * * * * * *

               *               
              * *              
             *   *             
            * * * *            
           *       *           
          * *     * *          
         *   *   *   *         
        * * * * * * * *        
       *       *       *       
      * *     * *     * *      
     *   *   *   *   *   *     
    * * * * * * * * * * * *    
   *       *       *       *   
  * *     * *     * *     * *  
 *   *   *   *   *   *   *   * 
* * * * * * * * * * * * * * * *

Hope that will help you, and comment if you have further questions. : )