Think of design as being similar to planning a trip. Given a specific destination, how do I get there from where I am now? I can better understand what I need to do by working a small example by hand.<\/p>\n\n\n\n
\n 1 2 3 4 \n --------------------\n 1 | 1 2 3 4 \n 2 | 2 4 6 8 \n 3 | 3 6 9 12 \n 4 | 4 8 12 16 \n<\/pre><\/div>\n\n\nTo produce this, I took each row number in the left-hand column and multiplied by the row of numbers across the top. So the first row of products is <\/p>\n\n\n
\n 1 x (1, 2, 3, 4) = (1, 2, 3, 4)\n<\/pre><\/div>\n\n\nthe second row is <\/p>\n\n\n
\n 2 x (1, 2, 3, 4) = (2, 4, 6, 8)\n<\/pre><\/div>\n\n\nand so forth. This may seem obvious given how young you probably were when you were first exposed to multiplication tables, but by doing this I am trying to understand my decision-making process while producing the table. I can see that I repeat the process of multiplying a number by the numbers 1 to n. The number than I multiply by each row of numbers is the row number itself-row 1, row 2, and so forth.<\/p>\n\n\n\n
I can see that I have a two processes that repeat and therefore I will probably need two loops. One loop produces the integers from 1 to n with each being multiplied by the row number. The other loop produces the row numbers, which themselves are the integers from 1 to n. The loop that produces the row numbers will be the outer loop, with the other loop being inside of it.<\/p>\n\n\n\n
At this point I have the function<\/p>\n\n\n
\ndef multTable(n) :\n for r in range(1, n+1) :\n for c in range(1, n+1) :\n print("%3d " % (r*c), end="")\n\n print()\n<\/pre><\/div>\n\n\nthat produces<\/p>\n\n\n
\n 1 2 3 4 \n 2 4 6 8 \n 3 6 9 12 \n 4 8 12 16\n<\/pre><\/div>\n\n\nThis is my starting point. Now I want to add the row and column numbers that make it look like a traditional multiplication table.f What should I do first? Since printing the column values will require indenting the output with spaces, I want to do that after I see how much space the row numbers require.<\/p>\n\n\n\n
Before printing a row of output value, that is, the products, I need to print the row number followed by the vertical bar. By default the print() function includes a newline, so I suppress it using end=””. Then the row of products will follow the line number. At this point my function looks like this:<\/p>\n\n\n
\ndef multTable(n) :\n for r in range(1, n+1) :\n print("%2d |" % r, end="")\n for c in range(1, n+1) :\n print("%3d " % (r*c), end="")\n\n print()\n\n<\/pre><\/div>\n\n\nand it produces<\/p>\n\n\n
\n 1 | 1 2 3 4 \n 2 | 2 4 6 8 \n 3 | 3 6 9 12 \n 4 | 4 8 12 16 \n<\/pre><\/div>\n\n\nNow I am ready to add the column numbers and a row of dashes to form a line. For this, I decided to create a separate function:<\/p>\n\n\n
\ndef printHeader(n) :\n print(" ", end="")\n\n for c in range(1, n+1) :\n print("%3d " % c, end="")\n\n print()\n\n print(" ", end="")\n\n for c in range(1, n+1) :\n print("-----", end="")\n\n print()\n<\/pre><\/div>\n\n\nMuch of the logic in printHeader()<\/code> is similar to what I wrote in multTable()<\/code>. Could I have put the logic of printHeader()<\/code> inside multTable()<\/code> instead of it’s own function? Sure, but I think this makes the underlying logic easier to follow. \n It also has the benefit that I can “turn off” the header if I wish by simply commenting out the function call.<\/p>\n\n\n\nHere is the final program:<\/p>\n\n\n
\ndef printHeader(n) :\n print(" ", end="")\n\n for c in range(1, n+1) :\n print("%3d " % c, end="")\n\n print()\n\n print(" ", end="")\n\n for c in range(1, n+1) :\n print("-----", end="")\n\n print()\n\n\ndef multTable(n) :\n printHeader(n)\n\n for r in range(1, n+1) :\n print("%2d |" % r, end="")\n for c in range(1, n+1) :\n print("%3d " % (r*c), end="")\n\n print()\n\n####### main #######\nn = int( input("enter size (15 rows max): ") )\n\nmultTable(n)\n\n<\/pre><\/div>","protected":false},"excerpt":{"rendered":"People learning to program often struggle with how to decompose a problem into the steps necessary to write a program to solve that problem. This is one of a series of posts in which I take a problem and go through my decision-making process that leads to a program. The problem: produce a multiplication table. I assume that at this point you know about statements, conditionals, loops, and functions. You can find a video with more details at https:\/\/youtu.be\/QJqfYn_4pmw. Design…<\/p>\n
Read More Read More<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[9,5],"tags":[],"class_list":["post-137","post","type-post","status-publish","format-standard","hentry","category-programming","category-python-programming"],"_links":{"self":[{"href":"https:\/\/www.brezeale.com\/index.php?rest_route=\/wp\/v2\/posts\/137","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.brezeale.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.brezeale.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.brezeale.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.brezeale.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=137"}],"version-history":[{"count":11,"href":"https:\/\/www.brezeale.com\/index.php?rest_route=\/wp\/v2\/posts\/137\/revisions"}],"predecessor-version":[{"id":296,"href":"https:\/\/www.brezeale.com\/index.php?rest_route=\/wp\/v2\/posts\/137\/revisions\/296"}],"wp:attachment":[{"href":"https:\/\/www.brezeale.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=137"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.brezeale.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=137"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.brezeale.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=137"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}