{"id":1132934,"date":"2025-01-08T21:01:50","date_gmt":"2025-01-08T13:01:50","guid":{"rendered":"https:\/\/docs.pingcode.com\/ask\/ask-ask\/1132934.html"},"modified":"2025-01-08T21:01:52","modified_gmt":"2025-01-08T13:01:52","slug":"python%e4%b8%ad%e5%a6%82%e4%bd%95%e6%b1%82%e4%b8%80%e4%b8%aa%e5%88%97%e8%a1%a8%e7%9a%84%e9%95%bf%e5%ba%a6","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/1132934.html","title":{"rendered":"python\u4e2d\u5982\u4f55\u6c42\u4e00\u4e2a\u5217\u8868\u7684\u957f\u5ea6"},"content":{"rendered":"

\"python\u4e2d\u5982\u4f55\u6c42\u4e00\u4e2a\u5217\u8868\u7684\u957f\u5ea6\"<\/p>\n

\u5728Python\u4e2d\uff0c\u6c42\u4e00\u4e2a\u5217\u8868\u7684\u957f\u5ea6\u7684\u65b9\u6cd5\u4e3b\u8981\u6709\u4ee5\u4e0b\u51e0\u79cd\uff1a\u4f7f\u7528\u5185\u7f6e\u51fd\u6570len()<\/code>\u3001\u624b\u52a8\u904d\u5386\u5217\u8868\u3001\u4ee5\u53ca\u5229\u7528Python\u7684collections<\/code>\u6a21\u5757\u3002\u6700\u5e38\u89c1\u548c\u63a8\u8350\u7684\u65b9\u6cd5\u662f\u4f7f\u7528\u5185\u7f6e\u51fd\u6570len()<\/code>\uff0c\u56e0\u4e3a\u5b83\u662f\u6700\u7b80\u6d01\u548c\u9ad8\u6548\u7684\u3002<\/strong><\/p>\n<\/p>\n

\u4e00\u3001\u5185\u7f6e\u51fd\u6570len()<\/code><\/h3>\n<\/p>\n

Python\u63d0\u4f9b\u4e86\u4e00\u4e2a\u975e\u5e38\u7b80\u6d01\u7684\u5185\u7f6e\u51fd\u6570len()<\/code>\u6765\u83b7\u53d6\u5217\u8868\u7684\u957f\u5ea6\u3002\u8fd9\u4e2a\u65b9\u6cd5\u4e0d\u4ec5\u9002\u7528\u4e8e\u5217\u8868\uff0c\u4e5f\u9002\u7528\u4e8e\u5176\u4ed6\u6570\u636e\u7c7b\u578b\u5982\u5b57\u7b26\u4e32\u3001\u5143\u7ec4\u3001\u5b57\u5178\u7b49\u3002\u901a\u8fc7\u8c03\u7528len()<\/code>\u51fd\u6570\u5e76\u4f20\u5165\u5217\u8868\u4f5c\u4e3a\u53c2\u6570\uff0c\u4fbf\u53ef\u4ee5\u8f7b\u677e\u83b7\u53d6\u5217\u8868\u7684\u957f\u5ea6\u3002<\/p>\n<\/p>\n

my_list = [1, 2, 3, 4, 5]<\/p>\n
length = len(my_list)<\/p>\n
print(length)  # \u8f93\u51fa\uff1a5<\/p>\n
<\/code><\/pre>\n<\/p>\n
\u4f18\u70b9\uff1a<\/h4>\n<\/p>\n
    \n
  • \u7b80\u6d01\u3001\u6613\u8bfb<\/strong>\uff1alen()<\/code>\u51fd\u6570\u7684\u8bed\u6cd5\u975e\u5e38\u7b80\u5355\uff0c\u4ee3\u7801\u53ef\u8bfb\u6027\u9ad8\u3002<\/li>\n
  • \u9ad8\u6548<\/strong>\uff1alen()<\/code>\u51fd\u6570\u5728\u5185\u90e8\u5b9e\u73b0\u4e0a\u662f\u7ecf\u8fc7\u4f18\u5316\u7684\uff0c\u6027\u80fd\u4f18\u8d8a\u3002<\/li>\n
  • \u901a\u7528\u6027\u5f3a<\/strong>\uff1a\u53ef\u4ee5\u7528\u4e8e\u591a\u79cd\u6570\u636e\u7c7b\u578b\u3002<\/li>\n<\/ul>\n
    \u8be6\u7ec6\u63cf\u8ff0\uff1a<\/h4>\n<\/p>\n
    len()<\/code>\u662fPython\u5185\u7f6e\u51fd\u6570\u4e4b\u4e00\uff0c\u5b83\u7684\u6548\u7387\u975e\u5e38\u9ad8\uff0c\u56e0\u4e3a\u5b83\u76f4\u63a5\u4ece\u5bf9\u8c61\u5185\u90e8\u7684\u5c5e\u6027\u4e2d\u83b7\u53d6\u957f\u5ea6\u3002\u5728Python\u7684\u5217\u8868\u5bf9\u8c61\u4e2d\uff0c\u957f\u5ea6\u662f\u5b58\u50a8\u5728\u4e00\u4e2a\u56fa\u5b9a\u7684\u4f4d\u7f6e\u4e0a\u7684\uff0c\u56e0\u6b64\u8c03\u7528len()<\/code>\u51fd\u6570\u51e0\u4e4e\u662f\u4e00\u4e2a\u5e38\u6570\u65f6\u95f4\u64cd\u4f5c\uff08O(1)\uff09\u3002\u8fd9\u4f7f\u5f97\u5b83\u975e\u5e38\u9002\u5408\u5728\u4efb\u4f55\u9700\u8981\u83b7\u53d6\u957f\u5ea6\u7684\u573a\u666f\u4e0b\u4f7f\u7528\u3002<\/p>\n<\/p>\n
    \u4e8c\u3001\u624b\u52a8\u904d\u5386\u5217\u8868<\/h3>\n<\/p>\n
    \u867d\u7136\u4e0d\u5982len()<\/code>\u51fd\u6570\u7b80\u6d01\uff0c\u4f46\u4f60\u4e5f\u53ef\u4ee5\u901a\u8fc7\u624b\u52a8\u904d\u5386\u5217\u8868\u6765\u8ba1\u7b97\u5176\u957f\u5ea6\u3002\u8fd9\u79cd\u65b9\u6cd5\u4e3b\u8981\u7528\u4e8e\u6559\u5b66\u6216\u7406\u89e3\u57fa\u672c\u7b97\u6cd5\u539f\u7406\u65f6\u3002<\/p>\n<\/p>\n
    my_list = [1, 2, 3, 4, 5]<\/p>\n
    length = 0<\/p>\n
    for item in my_list:<\/p>\n
        length += 1<\/p>\n
    print(length)  # \u8f93\u51fa\uff1a5<\/p>\n
    <\/code><\/pre>\n<\/p>\n
    \u4f18\u70b9\uff1a<\/h4>\n<\/p>\n
      \n
    • \u9002\u7528\u4e8e\u6559\u5b66<\/strong>\uff1a\u901a\u8fc7\u624b\u52a8\u8ba1\u7b97\u957f\u5ea6\uff0c\u53ef\u4ee5\u5e2e\u52a9\u7406\u89e3\u57fa\u672c\u7684\u8fed\u4ee3\u548c\u8ba1\u6570\u539f\u7406\u3002<\/li>\n
    • \u7075\u6d3b\u6027<\/strong>\uff1a\u53ef\u4ee5\u5728\u904d\u5386\u8fc7\u7a0b\u4e2d\u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c\uff0c\u5982\u8fc7\u6ee4\u6216\u8f6c\u6362\u3002<\/li>\n<\/ul>\n
      \u7f3a\u70b9\uff1a<\/h4>\n<\/p>\n
        \n
      • \u7e41\u7410<\/strong>\uff1a\u9700\u8981\u7f16\u5199\u989d\u5916\u7684\u4ee3\u7801\uff0c\u964d\u4f4e\u4e86\u4ee3\u7801\u7684\u53ef\u8bfb\u6027\u3002<\/li>\n
      • \u6027\u80fd\u8f83\u4f4e<\/strong>\uff1a\u76f8\u6bd4len()<\/code>\u51fd\u6570\uff0c\u624b\u52a8\u904d\u5386\u7684\u6027\u80fd\u8f83\u5dee\uff0c\u65f6\u95f4\u590d\u6742\u5ea6\u4e3aO(n)\u3002<\/li>\n<\/ul>\n
        \u4e09\u3001\u5229\u7528collections<\/code>\u6a21\u5757<\/h3>\n<\/p>\n
        Python\u7684collections<\/code>\u6a21\u5757\u63d0\u4f9b\u4e86\u591a\u79cd\u9ad8\u6548\u7684\u6570\u636e\u7ed3\u6784\uff0c\u4f46\u5bf9\u4e8e\u83b7\u53d6\u5217\u8868\u957f\u5ea6\uff0clen()<\/code>\u51fd\u6570\u4f9d\u7136\u662f\u6700\u7b80\u6d01\u548c\u9ad8\u6548\u7684\u9009\u62e9\u3002\u5728\u67d0\u4e9b\u7279\u6b8a\u573a\u666f\u4e0b\uff0c\u53ef\u80fd\u4f1a\u7528\u5230collections<\/code>\u6a21\u5757\u4e2d\u7684\u5176\u4ed6\u529f\u80fd\uff0c\u4f46\u5b83\u4eec\u5e76\u4e0d\u662f\u4e3a\u4e86\u66ff\u4ee3len()<\/code>\u51fd\u6570\u800c\u8bbe\u8ba1\u7684\u3002<\/p>\n<\/p>\n
        from collections import Counter<\/p>\n
        my_list = [1, 2, 3, 4, 5]<\/p>\n
        length = sum(Counter(my_list).values())<\/p>\n
        print(length)  # \u8f93\u51fa\uff1a5<\/p>\n
        <\/code><\/pre>\n<\/p>\n
        \u4f18\u70b9\uff1a<\/h4>\n<\/p>\n
          \n
        • \u529f\u80fd\u5f3a\u5927<\/strong>\uff1acollections<\/code>\u6a21\u5757\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5904\u7406\u590d\u6742\u7684\u6570\u636e\u64cd\u4f5c\u3002<\/li>\n
        • \u9002\u7528\u4e8e\u590d\u6742\u573a\u666f<\/strong>\uff1a\u5728\u9700\u8981\u8fdb\u884c\u7edf\u8ba1\u6216\u5176\u4ed6\u590d\u6742\u64cd\u4f5c\u65f6\u975e\u5e38\u6709\u7528\u3002<\/li>\n<\/ul>\n
          \u7f3a\u70b9\uff1a<\/h4>\n<\/p>\n
            \n
          • \u8fc7\u4e8e\u590d\u6742<\/strong>\uff1a\u5bf9\u4e8e\u7b80\u5355\u7684\u83b7\u53d6\u5217\u8868\u957f\u5ea6\u7684\u9700\u6c42\uff0c\u663e\u5f97\u8fc7\u4e8e\u590d\u6742\u3002<\/li>\n
          • \u6027\u80fd\u5f00\u9500<\/strong>\uff1a\u76f8\u6bd4len()<\/code>\u51fd\u6570\uff0c\u4f7f\u7528collections<\/code>\u6a21\u5757\u7684\u65b9\u6cd5\u6027\u80fd\u8f83\u4f4e\u3002<\/li>\n<\/ul>\n
            \u56db\u3001\u5e94\u7528\u573a\u666f\u548c\u6700\u4f73\u5b9e\u8df5<\/h3>\n<\/p>\n
            \u6570\u636e\u5206\u6790<\/h4>\n<\/p>\n
            \u5728\u6570\u636e\u5206\u6790\u4e2d\uff0c\u7ecf\u5e38\u9700\u8981\u83b7\u53d6\u6570\u636e\u96c6\u7684\u957f\u5ea6\u6765\u8fdb\u884c\u7edf\u8ba1\u548c\u5206\u6790\u3002\u4f7f\u7528len()<\/code>\u51fd\u6570\u53ef\u4ee5\u5feb\u901f\u83b7\u53d6\u6570\u636e\u96c6\u7684\u5927\u5c0f\uff0c\u4ece\u800c\u51b3\u5b9a\u540e\u7eed\u7684\u5904\u7406\u6b65\u9aa4\u3002<\/p>\n<\/p>\n
            import pandas as pd<\/p>\n
            data = pd.read_csv('data.csv')<\/p>\n
            num_rows = len(data)<\/p>\n
            print(f"\u6570\u636e\u96c6\u5305\u542b {num_rows} \u884c\u3002")<\/p>\n
            <\/code><\/pre>\n<\/p>\n
            Web\u5f00\u53d1<\/h4>\n<\/p>\n
            \u5728Web\u5f00\u53d1\u4e2d\uff0c\u5904\u7406\u8bf7\u6c42\u53c2\u6570\u6216\u8868\u5355\u6570\u636e\u65f6\uff0c\u53ef\u80fd\u9700\u8981\u83b7\u53d6\u5217\u8868\u7684\u957f\u5ea6\u6765\u9a8c\u8bc1\u6570\u636e\u7684\u5b8c\u6574\u6027\u3002\u4f8b\u5982\uff0c\u68c0\u67e5\u7528\u6237\u63d0\u4ea4\u7684\u591a\u9009\u9898\u7b54\u6848\u6570\u91cf\u662f\u5426\u7b26\u5408\u8981\u6c42\u3002<\/p>\n<\/p>\n
            def validate_form(answers):<\/p>\n
                if len(answers) != expected_length:<\/p>\n
                    return False<\/p>\n
                # \u5176\u4ed6\u9a8c\u8bc1\u903b\u8f91<\/p>\n
                return True<\/p>\n
            <\/code><\/pre>\n<\/p>\n
            \u79d1\u5b66\u8ba1\u7b97<\/h4>\n<\/p>\n
            \u5728\u79d1\u5b66\u8ba1\u7b97\u4e2d\uff0c\u77e9\u9635\u548c\u5411\u91cf\u7684\u7ef4\u5ea6\u662f\u975e\u5e38\u91cd\u8981\u7684\u4fe1\u606f\u3002\u901a\u8fc7\u83b7\u53d6\u5217\u8868\u957f\u5ea6\uff0c\u53ef\u4ee5\u786e\u5b9a\u77e9\u9635\u7684\u884c\u6570\u6216\u5411\u91cf\u7684\u5927\u5c0f\uff0c\u4ece\u800c\u8fdb\u884c\u77e9\u9635\u8fd0\u7b97\u6216\u5176\u4ed6\u79d1\u5b66\u8ba1\u7b97\u3002<\/p>\n<\/p>\n
            import numpy as np<\/p>\n
            vector = np.array([1, 2, 3, 4, 5])<\/p>\n
            length = len(vector)<\/p>\n
            print(f"\u5411\u91cf\u7684\u957f\u5ea6\u662f {length}\u3002")<\/p>\n
            <\/code><\/pre>\n<\/p>\n
            \u4e94\u3001\u6027\u80fd\u5bf9\u6bd4<\/h3>\n<\/p>\n
            \u5728\u6027\u80fd\u65b9\u9762\uff0clen()<\/code>\u51fd\u6570\u65e0\u7591\u662f\u83b7\u53d6\u5217\u8868\u957f\u5ea6\u7684\u6700\u4f73\u9009\u62e9\u3002\u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u6027\u80fd\u6bd4\u8f83\uff0c\u901a\u8fc7timeit<\/code>\u6a21\u5757\u6d4b\u8bd5\u4e0d\u540c\u65b9\u6cd5\u7684\u6267\u884c\u65f6\u95f4\u3002<\/p>\n<\/p>\n
            import timeit<\/p>\n
            setup = "my_list = [1, 2, 3, 4, 5]"<\/p>\n
            len() \u65b9\u6cd5<\/strong><\/h2>\n
            len_time = timeit.timeit('len(my_list)', setup=setup, number=1000000)<\/p>\n
            \u624b\u52a8\u904d\u5386<\/strong><\/h2>\n
            manual_time = timeit.timeit('length = 0\\nfor item in my_list:\\n    length += 1', setup=setup, number=1000000)<\/p>\n
            print(f"len() \u65b9\u6cd5\u8017\u65f6: {len_time}")<\/p>\n
            print(f"\u624b\u52a8\u904d\u5386\u8017\u65f6: {manual_time}")<\/p>\n
            <\/code><\/pre>\n<\/p>\n
            \u8fd0\u884c\u7ed3\u679c\u901a\u5e38\u663e\u793a\uff0clen()<\/code>\u65b9\u6cd5\u7684\u8017\u65f6\u663e\u8457\u4f4e\u4e8e\u624b\u52a8\u904d\u5386\u3002<\/p>\n<\/p>\n
            \u516d\u3001\u603b\u7ed3<\/h3>\n<\/p>\n
            \u7efc\u4e0a\u6240\u8ff0\uff0c\u83b7\u53d6Python\u5217\u8868\u957f\u5ea6\u6700\u7b80\u6d01\u548c\u9ad8\u6548\u7684\u65b9\u6cd5\u662f\u4f7f\u7528\u5185\u7f6e\u51fd\u6570len()<\/code>\u3002<\/strong>\u8fd9\u4e2a\u65b9\u6cd5\u4e0d\u4ec5\u8bed\u6cd5\u7b80\u5355\u3001\u53ef\u8bfb\u6027\u9ad8\uff0c\u800c\u4e14\u6027\u80fd\u4f18\u8d8a\uff0c\u9002\u7528\u4e8e\u5404\u79cd\u5e94\u7528\u573a\u666f\u3002\u867d\u7136\u624b\u52a8\u904d\u5386\u548ccollections<\/code>\u6a21\u5757\u63d0\u4f9b\u4e86\u66ff\u4ee3\u65b9\u6848\uff0c\u4f46\u5b83\u4eec\u5e76\u4e0d\u9002\u5408\u5927\u591a\u6570\u5e38\u89c1\u9700\u6c42\u3002\u56e0\u6b64\uff0c\u63a8\u8350\u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\u4f18\u5148\u9009\u62e9len()<\/code>\u51fd\u6570\u6765\u83b7\u53d6\u5217\u8868\u957f\u5ea6\u3002<\/p>\n<\/p>\n
            \u76f8\u5173\u95ee\u7b54FAQs\uff1a<\/strong><\/h2>\n
             \u5982\u4f55\u5728Python\u4e2d\u83b7\u53d6\u5217\u8868\u7684\u5143\u7d20\u6570\u91cf\uff1f<\/strong>
            \u5728Python\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528\u5185\u7f6e\u7684len()<\/code>\u51fd\u6570\u6765\u83b7\u53d6\u5217\u8868\u7684\u957f\u5ea6\u3002\u53ea\u9700\u5c06\u5217\u8868\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9len()<\/code>\u51fd\u6570\uff0c\u5b83\u5c06\u8fd4\u56de\u5217\u8868\u4e2d\u5143\u7d20\u7684\u6570\u91cf\u3002\u4f8b\u5982\uff1a  <\/p>\n
            my_list = [1, 2, 3, 4, 5]\nlength = len(my_list)\nprint(length)  # \u8f93\u51fa: 5\n<\/code><\/pre>\n
            \u83b7\u53d6\u5217\u8868\u957f\u5ea6\u65f6\uff0c\u6709\u6ca1\u6709\u6ce8\u610f\u4e8b\u9879\uff1f<\/strong>
            \u5728\u4f7f\u7528len()<\/code>\u51fd\u6570\u65f6\uff0c\u786e\u4fdd\u4f20\u5165\u7684\u5bf9\u8c61\u662f\u4e00\u4e2a\u5217\u8868\u3002\u82e5\u4f20\u5165\u7684\u5bf9\u8c61\u4e0d\u662f\u5217\u8868\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u9519\u8bef\u6216\u8fd4\u56de\u4e0d\u51c6\u786e\u7684\u7ed3\u679c\u3002\u53ef\u4ee5\u4f7f\u7528isinstance()<\/code>\u51fd\u6570\u6765\u68c0\u67e5\u5bf9\u8c61\u7c7b\u578b\u3002\u4f8b\u5982\uff1a  <\/p>\n
            if isinstance(my_list, list):\n    length = len(my_list)\nelse:\n    print("\u8be5\u5bf9\u8c61\u4e0d\u662f\u4e00\u4e2a\u5217\u8868")\n<\/code><\/pre>\n
            \u5982\u679c\u5217\u8868\u662f\u5d4c\u5957\u7684\uff0c\u5982\u4f55\u8ba1\u7b97\u603b\u5143\u7d20\u6570\u91cf\uff1f<\/strong>
            \u5bf9\u4e8e\u5d4c\u5957\u5217\u8868\uff0clen()<\/code>\u51fd\u6570\u53ea\u80fd\u8fd4\u56de\u5916\u5c42\u5217\u8868\u7684\u957f\u5ea6\u3002\u5982\u679c\u5e0c\u671b\u8ba1\u7b97\u6240\u6709\u5143\u7d20\u7684\u603b\u6570\u91cf\uff0c\u53ef\u4ee5\u4f7f\u7528\u9012\u5f52\u7684\u65b9\u6cd5\u6216\u5217\u8868\u63a8\u5bfc\u5f0f\u3002\u4f8b\u5982\uff1a  <\/p>\n
            nested_list = [[1, 2], [3, 4, 5], [6]]\ntotal_length = sum(len(sublist) for sublist in nested_list)\nprint(total_length)  # \u8f93\u51fa: 6\n<\/code><\/pre>\n
            \u8fd9\u79cd\u65b9\u6cd5\u80fd\u591f\u7075\u6d3b\u5730\u5904\u7406\u4e0d\u540c\u5c42\u7ea7\u7684\u5d4c\u5957\u7ed3\u6784\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"\u5728Python\u4e2d\uff0c\u6c42\u4e00\u4e2a\u5217\u8868\u7684\u957f\u5ea6\u7684\u65b9\u6cd5\u4e3b\u8981\u6709\u4ee5\u4e0b\u51e0\u79cd\uff1a\u4f7f\u7528\u5185\u7f6e\u51fd\u6570len()\u3001\u624b\u52a8\u904d\u5386\u5217\u8868\u3001\u4ee5\u53ca\u5229\u7528Pyth […]","protected":false},"author":3,"featured_media":1132946,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[37],"tags":[],"acf":[],"_links":{"self":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/1132934"}],"collection":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/comments?post=1132934"}],"version-history":[{"count":"1","href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/1132934\/revisions"}],"predecessor-version":[{"id":1132951,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/1132934\/revisions\/1132951"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media\/1132946"}],"wp:attachment":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media?parent=1132934"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/categories?post=1132934"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/tags?post=1132934"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}