{"id":1907,"date":"2026-10-02T14:56:59","date_gmt":"2026-10-02T14:56:59","guid":{"rendered":"https:\/\/accelthinking.com\/?p=1907"},"modified":"2026-10-03T19:13:04","modified_gmt":"2026-10-03T19:13:04","slug":"python-2d-list-build-traverse","status":"publish","type":"post","link":"https:\/\/accelthinking.com\/zh_cn\/python-2d-list-build-traverse\/","title":{"rendered":"How Do You Build and Traverse a 2D List?"},"content":{"rendered":"<style>\nhtml,body,#page{background:#f8fafc!important}.site-header,.site-footer,#masthead,#colophon,.entry-header,.post-navigation,.comments-area{display:none!important}.entry-title{display:none!important}.site-content .ast-container{max-width:100%!important;padding:0!important}.entry-content{margin:0!important;line-height:1.5!important}.site-content,#content,#primary,#main,.ast-plain-container #primary{margin:0!important;padding:0!important;background:#f8fafc}.ast-article-single{padding:0!important}\n.ati-page,.ati-page 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class=\"ati-letter\" style=\"--i:2\">w<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:4\">D<\/span><span class=\"ati-letter\" style=\"--i:5\">o<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:7\">Y<\/span><span class=\"ati-letter\" style=\"--i:8\">o<\/span><span class=\"ati-letter\" style=\"--i:9\">u<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:11\">B<\/span><span class=\"ati-letter\" style=\"--i:12\">u<\/span><span class=\"ati-letter\" style=\"--i:13\">i<\/span><span class=\"ati-letter\" style=\"--i:14\">l<\/span><span class=\"ati-letter\" style=\"--i:15\">d<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:17\">a<\/span><span class=\"ati-letter\" style=\"--i:18\">n<\/span><span class=\"ati-letter\" style=\"--i:19\">d<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:21\">T<\/span><span class=\"ati-letter\" style=\"--i:22\">r<\/span><span class=\"ati-letter\" style=\"--i:23\">a<\/span><span class=\"ati-letter\" style=\"--i:24\">v<\/span><span class=\"ati-letter\" style=\"--i:25\">e<\/span><span class=\"ati-letter\" style=\"--i:26\">r<\/span><span class=\"ati-letter\" style=\"--i:27\">s<\/span><span class=\"ati-letter\" style=\"--i:28\">e<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:30\">a<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:32\">2<\/span><span class=\"ati-letter\" style=\"--i:33\">D<\/span><\/span> <span class=\"ati-word\"><span class=\"ati-letter\" style=\"--i:35\">L<\/span><span class=\"ati-letter\" style=\"--i:36\">i<\/span><span class=\"ati-letter\" style=\"--i:37\">s<\/span><span class=\"ati-letter\" style=\"--i:38\">t<\/span><span class=\"ati-letter\" style=\"--i:39\">?<\/span><\/span><\/span><\/h1>\n<p>Learn how to build, index, read, and traverse Python 2D lists while avoiding shared-row aliasing mistakes.<\/p>\n<div class=\"ati-article-meta\"><span>\u4f5c\u8005\uff1aBerny<\/span><span>October 2, 2026<\/span><\/div>\n<\/div>\n<aside class=\"ati-side\"><strong>Rows &amp; Columns<br>Nested Loops<br>Safe Construction<\/strong>\n<p>Use grid[row][col], build independent rows, and traverse every cell with nested loops.<\/p>\n<\/aside>\n<\/section>\n<section class=\"ati-hero ati-lang-zh\">\n<div>\n<p class=\"ati-label\">Python \u5b66\u4e60\u7b14\u8bb0<\/p>\n<h1 aria-label=\"Python \u4e8c\u7ef4\u5217\u8868\u600e\u4e48\u521b\u5efa\u548c\u904d\u5386\uff1f\">Python \u4e8c\u7ef4\u5217\u8868\u600e\u4e48\u521b\u5efa\u548c\u904d\u5386\uff1f<\/h1>\n<p>\u8bb2\u6e05 Python \u4e8c\u7ef4\u5217\u8868\u7684\u521b\u5efa\u3001\u7d22\u5f15\u3001\u8bfb\u5165\u4e0e\u904d\u5386\uff0c\u5e76\u907f\u5f00\u591a\u884c\u5171\u4eab\u540c\u4e00\u4e2a\u5217\u8868\u7684\u9677\u9631\u3002<\/p>\n<div class=\"ati-article-meta\"><span>\u4f5c\u8005\uff1aBerny<\/span><span>2026 \u5e74 10 \u6708 2 \u65e5<\/span><\/div>\n<\/div>\n<aside class=\"ati-side\"><strong>\u884c\u4e0e\u5217<br>\u5d4c\u5957\u5faa\u73af<br>\u5b89\u5168\u521b\u5efa<\/strong>\n<p>\u7528 grid[row][col] \u8868\u793a\u4f4d\u7f6e\uff0c\u72ec\u7acb\u521b\u5efa\u6bcf\u4e00\u884c\uff0c\u518d\u7528\u5d4c\u5957\u5faa\u73af\u904d\u5386\u6240\u6709\u683c\u5b50\u3002<\/p>\n<\/aside>\n<\/section>\n<section class=\"ati-article-shell\">\n<article class=\"ati-article-card\">\n<div class=\"ati-share-tools\" data-ati-share>\n<div class=\"ati-share-copy\">\n<p class=\"ati-share-kicker\">\u5206\u4eab\u8fd9\u7bc7\u6587\u7ae0<\/p>\n<p class=\"ati-share-note\">\u590d\u5236\u94fe\u63a5\u3001\u4f7f\u7528\u624b\u673a\u5206\u4eab\u3001\u7528\u5fae\u4fe1\u626b\u7801\uff0c\u6216\u901a\u8fc7\u90ae\u4ef6\u53d1\u9001\u3002<\/p>\n<\/div>\n<div class=\"ati-share-actions\">\n    <button type=\"button\" data-share-native>\u5206\u4eab<\/button><br>\n    <button type=\"button\" data-share-copy-link>\u590d\u5236\u94fe\u63a5<\/button><br>\n    <button type=\"button\" data-share-wechat>\u5fae\u4fe1\u4e8c\u7ef4\u7801<\/button><br>\n    <a data-share-email>\u90ae\u7bb1<\/a>\n  <\/div>\n<div class=\"ati-share-qr\" data-share-qr hidden>\n    <img loading=\"lazy\" data-share-qr-img alt=\"QR code for sharing this article\">\n<p>\u4f7f\u7528\u5fae\u4fe1\u626b\u7801\uff0c\u7136\u540e\u5206\u4eab\u6587\u7ae0\u94fe\u63a5\u3002<\/p>\n<\/div>\n<p class=\"ati-share-status\" data-share-status aria-live=\"polite\">\n<\/p><\/div>\n<div class=\"ati-article-content ati-lang-en\">\n<article class=\"ati-post-article\">\n<p>Maps, seating charts, score tables \u2014 many problems hand you a table instead of a single list. Beginners often get stuck here: the data clearly has rows and columns, but where does it go in the program? A 2D list is not mysterious at all: it is a \"list that holds several rows,\" and each row is itself a list. This article uses one small 2-by-3 example to show how to build one, read a cell, and visit every cell.<\/p>\n<h2>A Common Mistake<\/h2>\n<p>Look at this tempting shortcut first:<\/p>\n<pre><code class=\"language-python\">grid = [[0] * 3] * 2\ngrid[0][1] = 9\nprint(grid)<\/code><\/pre>\n<p>Many people expect <code>[[0, 9, 0], [0, 0, 0]]<\/code>, but the real output is:<\/p>\n<pre><code class=\"language-text\">[[0, 9, 0], [0, 9, 0]]<\/code><\/pre>\n<p>We only changed the first row, so why did both rows change? Because <code>[[0] * 3] * 2<\/code> copies not \"two rows\" but \"two references to the same row object.\" The two rows are the same row, so editing any cell shows up in both.<\/p>\n<p>Two more mistakes happen when reading a table. Forgetting <code>int()<\/code>: without it, every cell stays a string, and addition turns into string joining. Swapping the indexes: <code>grid[1][2]<\/code> is not \"row one, column two\" in everyday counting \u2014 it is the row numbered 1 and the column numbered 2, both counted from 0. Remember the order: <code>grid[row][col]<\/code>, row first, column second.<\/p>\n<h2>The Core Idea<\/h2>\n<p>A 2D list is a list of lists. Store this seating chart in a program:<\/p>\n<div class=\"ati-table-wrap\">\n<table>\n<thead>\n<tr>\n<th><\/th>\n<th>col 0<\/th>\n<th>col 1<\/th>\n<th>col 2<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>row 0<\/td>\n<td>4<\/td>\n<td>7<\/td>\n<td>2<\/td>\n<\/tr>\n<tr>\n<td>row 1<\/td>\n<td>9<\/td>\n<td>1<\/td>\n<td>5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>It looks like this:<\/p>\n<pre><code class=\"language-python\">grid = [\n    [4, 7, 2],\n    [9, 1, 5],\n]<\/code><\/pre>\n<p>Why two indexes? Because to find a person you first say which row they sit in (row), then which seat in that row (col). Read one cell with <code>grid[row][col]<\/code>: <code>grid[1][2]<\/code> is row 1, column 2, which is <code>5<\/code>; <code>grid[0][0]<\/code> is the top-left corner, which is <code>4<\/code>. For the whole table, <code>len(grid)<\/code> is the number of rows and <code>len(grid[0])<\/code> is the number of columns.<\/p>\n<h2>The Recommended Way to Build One<\/h2>\n<p>In contests, a table usually comes from input: the first line is the number of rows <code>r<\/code>, the second line is the number of columns <code>c<\/code>, followed by <code>r<\/code> lines of <code>c<\/code> numbers each.<\/p>\n<pre><code class=\"language-python\">r = int(input())\nc = int(input())\ngrid = []\n\nfor _ in range(r):\n    row = [int(x) for x in input().split()]\n    grid.append(row)<\/code><\/pre>\n<p>Read one line, convert to numbers, append one row \u2014 repeat <code>r<\/code> times and the grid is ready. If you prefer to create an empty table first and fill it later, the correct pattern is:<\/p>\n<pre><code class=\"language-python\">grid = [[0] * c for _ in range(r)]<\/code><\/pre>\n<p>The <code>for _ in range(r)<\/code> part makes every iteration produce a fresh list \u2014 that is the key, and it is exactly the fix for the shared-row trap above.<\/p>\n<h2>Visiting Every Cell<\/h2>\n<p>The outer loop controls rows, the inner loop controls columns, and together they visit each cell exactly once:<\/p>\n<pre><code class=\"language-python\">grid = [\n    [4, 7, 2],\n    [9, 1, 5],\n]\n\nfor row in range(len(grid)):\n    for col in range(len(grid[row])):\n        print(row, col, grid[row][col])<\/code><\/pre>\n<pre><code class=\"language-text\">0 0 4\n0 1 7\n0 2 2\n1 0 9\n1 1 1\n1 2 5<\/code><\/pre>\n<p>Finish the three cells of row 0 first, then move into row 1 \u2014 left to right, top to bottom, like reading a book. Once traversal is in place, summaries follow. To print the sum of each row:<\/p>\n<pre><code class=\"language-python\">for row in grid:\n    row_sum = 0\n    for value in row:\n        row_sum += value\n    print(row_sum)<\/code><\/pre>\n<pre><code class=\"language-text\">13\n15<\/code><\/pre>\n<p>For column sums, do it the other way around: fix one column, then add it from top to bottom, giving <code>13<\/code>, <code>8<\/code>, <code>7<\/code>. Watch where you reset the local <code>row_sum<\/code> \u2014 it must be cleared before starting each row, or the numbers merge into one running total.<\/p>\n<h2>Updating and Counting Cells<\/h2>\n<p>Updates and counts are just small variations of traversal. Add one to every cell:<\/p>\n<pre><code class=\"language-python\">for row in range(len(grid)):\n    for col in range(len(grid[row])):\n        grid[row][col] += 1<\/code><\/pre>\n<p>Counting \"how many cells equal the target\" is the same walk with a counter that increases on every match:<\/p>\n<pre><code class=\"language-python\">grid = [\n    [4, 7, 2],\n    [9, 1, 5],\n]\n\ntarget = 7\ncount = 0\n\nfor row in range(len(grid)):\n    for col in range(len(grid[row])):\n        if grid[row][col] == target:\n            count += 1\n\nprint(count)<\/code><\/pre>\n<pre><code class=\"language-text\">1<\/code><\/pre>\n<p>These are the same moves behind grid-style problems: a snail's path across cells, harvest counts on a farm, or triangular fields.<\/p>\n<h2>Compare the Options<\/h2>\n<div class=\"ati-table-wrap\">\n<table>\n<thead>\n<tr>\n<th>Pattern<\/th>\n<th>When to use it<\/th>\n<th>Watch out<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><code>[[0] * c] * r<\/code><\/td>\n<td>Looks quick<\/td>\n<td>All rows share one object; editing one cell changes every row. Do not use it.<\/td>\n<\/tr>\n<tr>\n<td><code>[[0] * c for _ in range(r)]<\/code><\/td>\n<td>Build first, fill later<\/td>\n<td>Each row is independent. Recommended.<\/td>\n<\/tr>\n<tr>\n<td>Read one row, then <code>append<\/code> it<\/td>\n<td>Contest input<\/td>\n<td>Remember <code>int()<\/code> for numeric cells, or they stay strings.<\/td>\n<\/tr>\n<tr>\n<td>Fix row and vary col \/ fix col and vary row<\/td>\n<td>Row sums \/ column sums<\/td>\n<td>Reset the accumulator before the loop it belongs to.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2>Practice<\/h2>\n<ol>\n<li>Basic: build <code>[[4, 7, 2], [9, 1, 5]]<\/code> and print <code>grid[1][2]<\/code>. (Answer: <code>5<\/code>)<\/li>\n<li>Variation: read <code>r<\/code>, <code>c<\/code>, and a numeric table, then print the sum of each row.<\/li>\n<li>Challenge: print the sum of each column, then the total of the whole table.<\/li>\n<\/ol>\n<h2>One-Sentence Takeaway<\/h2>\n<p>A 2D list is a list of lists: use <code>grid[row][col]<\/code>, row before column, and make every row a fresh list.<\/p>\n<p>If this article helped you sort out indexes and traversal, save it and practice along. To work on more grid-style problems, visit the Python Learning Notes channel on our website and follow the series step by step.<\/p>\n<\/article>\n<\/div>\n<div class=\"ati-article-content ati-lang-zh\">\n<article class=\"ati-post-article\">\n<p>\u5730\u56fe\u3001\u5ea7\u4f4d\u8868\u3001\u6210\u7ee9\u5355\u2014\u2014\u5f88\u591a\u9898\u76ee\u7ed9\u4f60\u7684\u6570\u636e\u4e0d\u662f\u4e00\u4e2a\u5217\u8868\uff0c\u800c\u662f\u4e00\u5f20\u8868\u683c\u3002\u65b0\u624b\u5e38\u5e38\u5361\u5728\u8fd9\u91cc\uff1a\u683c\u5b50\u660e\u660e\u6709\u884c\u6709\u5217\uff0c\u7a0b\u5e8f\u91cc\u5374\u4e0d\u77e5\u9053\u5f80\u54ea\u653e\u3002\u5176\u5b9e\u4e8c\u7ef4\u5217\u8868\u5e76\u4e0d\u795e\u79d8\uff1a\u5b83\u5c31\u662f\u4e00\u4e2a\u300c\u88c5\u7740\u82e5\u5e72\u884c\u7684\u5217\u8868\u300d\uff0c\u800c\u6bcf\u4e00\u884c\u672c\u8eab\u53c8\u662f\u4e00\u4e2a\u5217\u8868\u3002\u8fd9\u7bc7\u7528\u4e00\u4e2a 2 \u884c 3 \u5217\u7684\u5c0f\u4f8b\u5b50\uff0c\u8bb2\u6e05\u600e\u4e48\u521b\u5efa\u3001\u600e\u4e48\u53d6\u503c\u3001\u600e\u4e48\u4e00\u683c\u4e00\u683c\u904d\u5386\u3002<\/p>\n<h2>\u5e38\u89c1\u9519\u8bef<\/h2>\n<p>\u5148\u770b\u770b\u8fd9\u4e2a\u770b\u4f3c\u65b9\u4fbf\u7684\u5199\u6cd5\uff1a<\/p>\n<pre><code class=\"language-python\">grid = [[0] * 3] * 2\ngrid[0][1] = 9\nprint(grid)<\/code><\/pre>\n<p>\u5f88\u591a\u4eba\u4ee5\u4e3a\u4f1a\u6253\u5370 <code>[[0, 9, 0], [0, 0, 0]]<\/code>\uff0c\u5b9e\u9645\u7ed3\u679c\u5374\u662f\uff1a<\/p>\n<pre><code class=\"language-text\">[[0, 9, 0], [0, 9, 0]]<\/code><\/pre>\n<p>\u53ea\u6539\u4e86\u7b2c\u4e00\u884c\uff0c\u4e3a\u4ec0\u4e48\u4e24\u884c\u90fd\u53d8\u4e86\uff1f\u56e0\u4e3a <code>[[0] * 3] * 2<\/code> \u590d\u5236\u7684\u4e0d\u662f\u300c\u4e24\u884c\u300d\uff0c\u800c\u662f\u300c\u540c\u4e00\u4e2a\u884c\u5bf9\u8c61\u7684\u4e24\u4efd\u5f15\u7528\u300d\u2014\u2014\u4e24\u884c\u5176\u5b9e\u662f\u540c\u4e00\u884c\u3002\u6539\u4efb\u4f55\u4e00\u683c\uff0c\u4e24\u884c\u4e00\u8d77\u53d8\u3002<\/p>\n<p>\u8bfb\u8868\u683c\u65f6\u8fd8\u6709\u4e24\u4e2a\u9ad8\u9891\u9519\u8bef\u3002\u4e00\u662f\u5fd8\u8bb0\u628a\u8f93\u5165\u8f6c\u6210\u6570\u5b57\uff1a\u4e0d\u52a0 <code>int()<\/code>\uff0c\u683c\u5b50\u5168\u662f\u5b57\u7b26\u4e32\uff0c\u505a\u52a0\u6cd5\u4f1a\u53d8\u6210\u62fc\u5b57\u7b26\u4e32\u3002\u4e8c\u662f\u884c\u5217\u4e0b\u6807\u641e\u6df7\uff1a<code>grid[1][2]<\/code> \u4e0d\u662f\u300c\u7b2c 1 \u884c\u7b2c 2 \u5217\u300d\u7684\u81ea\u7136\u8bf4\u6cd5\uff0c\u800c\u662f\u300c\u4ece 0 \u6570\u8d77\u7684\u7b2c 1 \u884c\u3001\u7b2c 2 \u5217\u300d\u3002\u8bb0\u4f4f\u987a\u5e8f\u2014\u2014<code>grid[row][col]<\/code>\uff0c\u5148\u884c\u540e\u5217\u3002<\/p>\n<h2>\u6838\u5fc3\u6982\u5ff5<\/h2>\n<p>\u4e8c\u7ef4\u5217\u8868\u5c31\u662f\u5217\u8868\u5957\u5217\u8868\u3002\u628a\u8fd9\u5f20\u5ea7\u4f4d\u8868\u5b58\u8fdb\u7a0b\u5e8f\uff1a<\/p>\n<div class=\"ati-table-wrap\">\n<table>\n<thead>\n<tr>\n<th><\/th>\n<th>\u7b2c 0 \u5217<\/th>\n<th>\u7b2c 1 \u5217<\/th>\n<th>\u7b2c 2 \u5217<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u7b2c 0 \u884c<\/td>\n<td>4<\/td>\n<td>7<\/td>\n<td>2<\/td>\n<\/tr>\n<tr>\n<td>\u7b2c 1 \u884c<\/td>\n<td>9<\/td>\n<td>1<\/td>\n<td>5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>\u5199\u51fa\u6765\u5c31\u662f\uff1a<\/p>\n<pre><code class=\"language-python\">grid = [\n    [4, 7, 2],\n    [9, 1, 5],\n]<\/code><\/pre>\n<p>\u4e3a\u4ec0\u4e48\u8981\u4e24\u4e2a\u4e0b\u6807\uff1f\u56e0\u4e3a\u627e\u4e00\u4e2a\u4eba\uff0c\u8981\u5148\u8bf4\u4ed6\u5750\u7b2c\u51e0\u6392\uff08row\uff09\uff0c\u518d\u8bf4\u4ed6\u5728\u8fd9\u4e00\u6392\u7684\u7b2c\u51e0\u4e2a\u4f4d\u7f6e\uff08col\uff09\u3002\u53d6\u4e00\u4e2a\u683c\u5b50\u5c31\u5199 <code>grid[row][col]<\/code>\uff1a<code>grid[1][2]<\/code> \u662f\u7b2c 1 \u884c\u7684\u7b2c 2 \u5217\uff0c\u4e5f\u5c31\u662f <code>5<\/code>\uff1b<code>grid[0][0]<\/code> \u662f\u5de6\u4e0a\u89d2\uff0c\u4e5f\u5c31\u662f <code>4<\/code>\u3002\u4e24\u5f20\u8868\u62fc\u5728\u4e00\u8d77\uff0c<code>len(grid)<\/code> \u662f\u884c\u6570\uff0c<code>len(grid[0])<\/code> \u662f\u5217\u6570\u3002<\/p>\n<p>\u4e25\u683c\u8bf4\uff0c\u6bcf\u884c\u7684\u957f\u5ea6\u53ef\u4ee5\u4e0d\u4e00\u6837\uff0c\u4e8c\u7ef4\u5217\u8868\u5e76\u4e0d\u5f3a\u8feb\u8868\u683c\u6574\u9f50\u3002\u4f46\u7ade\u8d5b\u91cc\u7684\u8f93\u5165\u90fd\u4fdd\u8bc1\u662f\u77e9\u5f62\u8868\u683c\uff0c\u6240\u4ee5\u6309\u9898\u76ee\u7ed9\u7684\u884c\u5217\u6570\u5904\u7406\u5c31\u597d\uff0c\u522b\u81ea\u5df1\u989d\u5916\u52a0\u5224\u65ad\u3002<\/p>\n<h2>\u63a8\u8350\u5199\u6cd5<\/h2>\n<p>\u7ade\u8d5b\u91cc\u7684\u8868\u683c\u4e00\u822c\u4ece\u8f93\u5165\u8bfb\u8fdb\u6765\uff1a\u7b2c\u4e00\u884c\u662f\u884c\u6570 <code>r<\/code>\uff0c\u7b2c\u4e8c\u884c\u662f\u5217\u6570 <code>c<\/code>\uff0c\u63a5\u4e0b\u6765 <code>r<\/code> \u884c\uff0c\u6bcf\u884c <code>c<\/code> \u4e2a\u6570\u3002<\/p>\n<pre><code class=\"language-python\">r = int(input())\nc = int(input())\ngrid = []\n\nfor _ in range(r):\n    row = [int(x) for x in input().split()]\n    grid.append(row)<\/code><\/pre>\n<p>\u8bfb\u4e00\u884c\u3001\u8f6c\u6570\u5b57\u3001<code>append<\/code> \u4e00\u884c\uff0c\u5faa\u73af <code>r<\/code> \u6b21\uff0c\u8868\u683c\u5c31\u5efa\u597d\u4e86\u3002\u5982\u679c\u6253\u7b97\u5148\u5efa\u597d\u7a7a\u8868\u518d\u6162\u6162\u586b\uff0c\u6b63\u786e\u5199\u6cd5\u662f\uff1a<\/p>\n<pre><code class=\"language-python\">grid = [[0] * c for _ in range(r)]<\/code><\/pre>\n<p><code>for _ in range(r)<\/code> \u4f1a\u8ba9\u6bcf\u4e00\u8f6e\u90fd\u751f\u6210\u4e00\u4e2a\u65b0\u5217\u8868\uff0c\u8fd9\u624d\u662f\u5173\u952e\u2014\u2014\u5b83\u6b63\u662f\u524d\u9762\u90a3\u4e2a\u5171\u4eab\u884c\u9677\u9631\u7684\u89e3\u6cd5\u3002<\/p>\n<h2>\u904d\u5386\u6240\u6709\u683c\u5b50<\/h2>\n<p>\u5916\u5c42\u5faa\u73af\u7ba1\u884c\uff0c\u5185\u5c42\u5faa\u73af\u7ba1\u5217\uff0c\u4e24\u4e2a\u5faa\u73af\u5408\u8d77\u6765\u628a\u6bcf\u4e2a\u683c\u5b50\u6070\u597d\u8d70\u4e00\u904d\uff1a<\/p>\n<pre><code class=\"language-python\">grid = [\n    [4, 7, 2],\n    [9, 1, 5],\n]\n\nfor row in range(len(grid)):\n    for col in range(len(grid[row])):\n        print(row, col, grid[row][col])<\/code><\/pre>\n<pre><code class=\"language-text\">0 0 4\n0 1 7\n0 2 2\n1 0 9\n1 1 1\n1 2 5<\/code><\/pre>\n<p>\u5148\u8d70\u5b8c\u7b2c 0 \u884c\u7684\u4e09\u683c\uff0c\u518d\u8d70\u8fdb\u7b2c 1 \u884c\u2014\u2014\u50cf\u8bfb\u4e66\u4e00\u6837\u4ece\u5de6\u5230\u53f3\u3001\u4ece\u4e0a\u5230\u4e0b\u3002\u4ea4\u6362\u4e24\u5c42\u5faa\u73af\u7684\u987a\u5e8f\u4e5f\u80fd\u8d70\u5b8c\u6bcf\u4e2a\u683c\u5b50\uff0c\u4f46\u6309\u884c\u4f18\u5148\u6700\u4e0d\u5bb9\u6613\u628a\u81ea\u5df1\u7ed5\u6655\u3002\u904d\u5386\u6709\u4e86\uff0c\u7edf\u8ba1\u5c31\u987a\u4e86\u3002\u6bd4\u5982\u5206\u522b\u6c42\u6bcf\u4e00\u884c\u7684\u548c\uff1a<\/p>\n<pre><code class=\"language-python\">for row in grid:\n    row_sum = 0\n    for value in row:\n        row_sum += value\n    print(row_sum)<\/code><\/pre>\n<pre><code class=\"language-text\">13\n15<\/code><\/pre>\n<p>\u6c42\u5217\u548c\u5c31\u53cd\u8fc7\u6765\uff1a\u5148\u56fa\u5b9a\u4e00\u5217\uff0c\u518d\u628a\u8fd9\u4e00\u5217\u4ece\u4e0a\u5230\u4e0b\u52a0\u4e00\u904d\uff0c\u7ed3\u679c\u662f <code>13<\/code>\u3001<code>8<\/code>\u3001<code>7<\/code>\u3002\u6ce8\u610f\u5c40\u90e8\u53d8\u91cf <code>row_sum<\/code> \u8981\u5728\u300c\u8fdb\u5165\u6bcf\u4e00\u884c\u4e4b\u524d\u300d\u6e05\u96f6\uff1b\u6e05\u9519\u4e86\u4f4d\u7f6e\uff0c\u6570\u5b57\u5c31\u4f1a\u7d2f\u52a0\u5230\u4e00\u8d77\u3002<\/p>\n<h2>\u6539\u683c\u5b50\u3001\u6570\u683c\u5b50<\/h2>\n<p>\u66f4\u65b0\u548c\u8ba1\u6570\u53ea\u662f\u904d\u5386\u7684\u5c0f\u53d8\u79cd\u3002\u8ba9\u6240\u6709\u683c\u5b50\u7684\u503c\u52a0\u4e00\uff1a<\/p>\n<pre><code class=\"language-python\">for row in range(len(grid)):\n    for col in range(len(grid[row])):\n        grid[row][col] += 1<\/code><\/pre>\n<p>\u6570\u300c\u6709\u591a\u5c11\u683c\u7b49\u4e8e\u76ee\u6807\u503c\u300d\u4e5f\u4e00\u6837\u8d70\u4e00\u904d\uff0c\u78b0\u5230\u76f8\u7b49\u5c31\u8ba9\u8ba1\u6570\u5668\u52a0\u4e00\uff1a<\/p>\n<pre><code class=\"language-python\">grid = [\n    [4, 7, 2],\n    [9, 1, 5],\n]\n\ntarget = 7\ncount = 0\n\nfor row in range(len(grid)):\n    for col in range(len(grid[row])):\n        if grid[row][col] == target:\n            count += 1\n\nprint(count)<\/code><\/pre>\n<pre><code class=\"language-text\">1<\/code><\/pre>\n<p>\u8fd9\u4e9b\u6b63\u662f\u5730\u56fe\u7c7b\u3001\u7f51\u683c\u7c7b\u9898\u76ee\u2014\u2014\u6bd4\u5982\u8717\u725b\u722c\u8fc7\u7684\u683c\u5b50\u3001\u519c\u7530\u6536\u6210\u3001\u4e09\u89d2\u5f62\u7530\u5730\u2014\u2014\u80cc\u540e\u7684\u540c\u4e00\u5957\u52a8\u4f5c\u3002<\/p>\n<h2>\u5bf9\u6bd4\u4e00\u4e0b<\/h2>\n<div class=\"ati-table-wrap\">\n<table>\n<thead>\n<tr>\n<th>\u5199\u6cd5<\/th>\n<th>\u9002\u5408\u60c5\u51b5<\/th>\n<th>\u6ce8\u610f\u70b9<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><code>[[0] * c] * r<\/code><\/td>\n<td>\u770b\u8d77\u6765\u7701\u4e8b<\/td>\n<td>\u6240\u6709\u884c\u5171\u4eab\u540c\u4e00\u5bf9\u8c61\uff0c\u6539\u4e00\u683c\u5168\u53d8\uff0c\u4e0d\u8981\u7528<\/td>\n<\/tr>\n<tr>\n<td><code>[[0] * c for _ in range(r)<\/code><\/td>\n<td>\u5148\u5efa\u8868\u3001\u540e\u586b\u503c<\/td>\n<td>\u6bcf\u884c\u72ec\u7acb\uff0c\u63a8\u8350<\/td>\n<\/tr>\n<tr>\n<td>\u8bfb\u4e00\u884c <code>append<\/code> \u4e00\u884c<\/td>\n<td>\u7ade\u8d5b\u8f93\u5165<\/td>\n<td>\u6570\u5b57\u683c\u5b50\u8bb0\u5f97 <code>int()<\/code>\uff0c\u5426\u5219\u662f\u5b57\u7b26\u4e32<\/td>\n<\/tr>\n<tr>\n<td>\u56fa\u5b9a row \u53d8 col \/ \u56fa\u5b9a col \u53d8 row<\/td>\n<td>\u6c42\u884c\u548c \/ \u6c42\u5217\u548c<\/td>\n<td>\u6c42\u548c\u7684\u53d8\u91cf\u8981\u5728\u6b63\u786e\u7684\u5faa\u73af\u524d\u6e05\u96f6<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2>\u5c0f\u7ec3\u4e60<\/h2>\n<ol>\n<li>\u57fa\u7840\u9898\uff1a\u5efa\u51fa <code>[[4, 7, 2], [9, 1, 5]]<\/code>\uff0c\u6253\u5370 <code>grid[1][2]<\/code>\u3002\uff08\u7b54\u6848\uff1a<code>5<\/code>\uff09<\/li>\n<li>\u53d8\u5f0f\u9898\uff1a\u8bfb\u5165 <code>r<\/code>\u3001<code>c<\/code> \u548c\u4e00\u4e2a\u6570\u5b57\u8868\u683c\uff0c\u8f93\u51fa\u6bcf\u4e00\u884c\u7684\u548c\u3002<\/li>\n<li>\u6311\u6218\u9898\uff1a\u8f93\u51fa\u6bcf\u4e00\u5217\u7684\u548c\uff0c\u518d\u8f93\u51fa\u6574\u5f20\u8868\u683c\u7684\u603b\u548c\u3002<\/li>\n<\/ol>\n<h2>\u4e00\u53e5\u8bdd\u8bb0\u4f4f<\/h2>\n<p>\u4e8c\u7ef4\u5217\u8868\u5c31\u662f\u5217\u8868\u5957\u5217\u8868\uff1a<code>grid[row][col]<\/code>\uff0c\u5148\u884c\u540e\u5217\uff0c\u4e00\u884c\u4e00\u4e2a\u65b0\u5217\u8868\u3002<\/p>\n<p>\u5982\u679c\u8fd9\u7bc7\u5e2e\u4f60\u7406\u987a\u4e86\u4e0b\u6807\u548c\u904d\u5386\uff0c\u6b22\u8fce\u6536\u85cf\u8d77\u6765\u7167\u7740\u7ec3\u3002\u60f3\u52a8\u624b\u505a\u66f4\u591a\u8868\u683c\u7c7b\u7684\u9898\u76ee\uff0c\u53ef\u4ee5\u5230\u5b98\u7f51 Python Learning Notes \u9891\u9053\uff0c\u8ddf\u7740\u7cfb\u5217\u7b14\u8bb0\u4e00\u6b65\u4e00\u6b65\u6765\u3002<\/p>\n<\/article>\n<\/div>\n<section class=\"ati-feedback-cta ati-lang-en\" data-ati-feedback>\n<div class=\"ati-feedback-copy\">\n<p class=\"ati-feedback-title\">\u6709\u95ee\u9898\u6216\u5efa\u8bae\uff1f<\/p>\n<p class=\"ati-feedback-note\">\u5982\u679c\u4f60\u5bf9\u672c\u6587\u6709\u7591\u95ee\uff0c\u6216\u5e0c\u671b\u63d0\u51fa\u6539\u8fdb\u5efa\u8bae\uff0c\u8bf7\u7ed9\u6211\u4eec\u53d1\u9001\u79c1\u5bc6\u7559\u8a00\u3002<\/p>\n<\/div>\n<p>  <a class=\"ati-feedback-button\" href=\"\/zh_cn\/contact\/\" data-ati-feedback-link>\u53d1\u9001\u53cd\u9988<\/a><br>\n<\/p><\/section>\n<section class=\"ati-feedback-cta ati-lang-zh\" data-ati-feedback>\n<div class=\"ati-feedback-copy\">\n<p class=\"ati-feedback-title\">\u6709\u95ee\u9898\u6216\u5efa\u8bae\uff1f<\/p>\n<p class=\"ati-feedback-note\">\u5982\u679c\u4f60\u5bf9\u672c\u6587\u6709\u7591\u95ee\uff0c\u6216\u5e0c\u671b\u63d0\u51fa\u6539\u8fdb\u5efa\u8bae\uff0c\u8bf7\u7ed9\u6211\u4eec\u53d1\u9001\u79c1\u5bc6\u7559\u8a00\u3002<\/p>\n<\/div>\n<p>  <a class=\"ati-feedback-button\" href=\"\/zh_cn\/contact\/\" 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