{"id":1004222,"date":"2024-12-27T10:24:26","date_gmt":"2024-12-27T02:24:26","guid":{"rendered":"https:\/\/docs.pingcode.com\/ask\/ask-ask\/1004222.html"},"modified":"2024-12-27T10:24:30","modified_gmt":"2024-12-27T02:24:30","slug":"python-%e5%a6%82%e4%bd%95%e8%a1%a8%e7%a4%ba%e7%a9%ba%e5%80%bc","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/1004222.html","title":{"rendered":"python \u5982\u4f55\u8868\u793a\u7a7a\u503c"},"content":{"rendered":"<p style=\"text-align:center;\" ><img decoding=\"async\" src=\"https:\/\/cdn-kb.worktile.com\/kb\/wp-content\/uploads\/2024\/04\/25081237\/ab5fd17a-b1cd-4764-8ca6-6074b884a353.webp\" alt=\"python \u5982\u4f55\u8868\u793a\u7a7a\u503c\" \/><\/p>\n<p><p> <strong>\u5728Python\u4e2d\uff0c\u7a7a\u503c\u901a\u5e38\u4f7f\u7528<code>None<\/code>\u8868\u793a\u3001<code>None<\/code>\u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u5e38\u91cf\u3001\u7528\u6765\u8868\u793a\u7a7a\u3001\u6216\u6ca1\u6709\u503c\u7684\u72b6\u6001\u3001\u5728\u53d8\u91cf\u58f0\u660e\u3001\u51fd\u6570\u8fd4\u56de\u65e0\u7ed3\u679c\u6216\u521d\u59cb\u5316\u65f6\u4f7f\u7528<\/strong>\u3002<code>None<\/code>\u662f\u4e00\u4e2a\u5bf9\u8c61\uff0c\u56e0\u6b64\u5b83\u4e0e\u5176\u4ed6\u57fa\u672c\u7c7b\u578b\uff08\u5982\u6574\u6570\u3001\u5b57\u7b26\u4e32\u7b49\uff09\u4e0d\u540c\u3002\u5b83\u5728\u903b\u8f91\u8fd0\u7b97\u4e2d\u88ab\u89c6\u4e3aFalse\uff0c\u4f46\u5b83\u672c\u8eab\u5e76\u4e0d\u7b49\u4e8eFalse\u30010\u6216\u7a7a\u5b57\u7b26\u4e32\u3002<code>None<\/code>\u7684\u4f7f\u7528\u4f7f\u5f97\u4ee3\u7801\u66f4\u52a0\u6e05\u6670\uff0c\u5c24\u5176\u662f\u5728\u9700\u8981\u663e\u5f0f\u8868\u793a\u201c\u65e0\u503c\u201d\u65f6\u3002<\/p>\n<\/p>\n<p><p><code>None<\/code>\u6700\u5e38\u7528\u7684\u573a\u666f\u4e4b\u4e00\u662f\u5728\u51fd\u6570\u4e2d\u3002\u5728Python\u4e2d\uff0c\u5982\u679c\u4e00\u4e2a\u51fd\u6570\u6ca1\u6709\u8fd4\u56de\u503c\uff0c\u9ed8\u8ba4\u4f1a\u8fd4\u56de<code>None<\/code>\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">def example_function():<\/p>\n<p>    pass<\/p>\n<p>result = example_function()<\/p>\n<p>print(result)  # \u8f93\u51fa: None<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u6b64\u5916\uff0c<code>None<\/code>\u4e5f\u5e38\u7528\u4e8e\u521d\u59cb\u5316\u53d8\u91cf\uff0c\u5c24\u5176\u662f\u5728\u9700\u8981\u7a0d\u540e\u518d\u7ed9\u53d8\u91cf\u8d4b\u503c\u7684\u60c5\u51b5\u4e0b\u3002\u8fd9\u79cd\u505a\u6cd5\u53ef\u4ee5\u63d0\u9ad8\u4ee3\u7801\u7684\u53ef\u8bfb\u6027\uff0c\u5e76\u4e14\u660e\u786e\u8868\u660e\u8be5\u53d8\u91cf\u5c1a\u672a\u6301\u6709\u4efb\u4f55\u6709\u6548\u6570\u636e\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">value = None<\/p>\n<h2><strong>\u5728\u67d0\u4e9b\u6761\u4ef6\u4e0b\u4e3avalue\u8d4b\u503c<\/strong><\/h2>\n<p>if some_condition:<\/p>\n<p>    value = compute_value()<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u4e00\u3001PYTHON \u4e2d\u7684 <code>None<\/code> \u7c7b\u578b<\/p>\n<\/p>\n<p><p><code>None<\/code> \u662f Python \u4e2d\u7684\u4e00\u4e2a\u7279\u6b8a\u7c7b\u578b\uff0c\u5b83\u8868\u793a\u6ca1\u6709\u503c\u6216\u7a7a\u503c\u3002\u5728\u8bb8\u591a\u7f16\u7a0b\u8bed\u8a00\u4e2d\uff0c\u8fd9\u79cd\u6982\u5ff5\u53ef\u80fd\u88ab\u79f0\u4e3a\u201cnull\u201d\u6216\u201cnil\u201d\u3002Python \u4f7f\u7528 <code>None<\/code> \u6765\u8868\u793a\u6ca1\u6709\u503c\u7684\u5bf9\u8c61\u6216\u53d8\u91cf\u3002 <code>None<\/code> \u662f\u4e00\u4e2a\u5355\u4f8b\u5bf9\u8c61\uff0c\u8fd9\u610f\u5473\u7740\u5728\u4e00\u4e2a\u8fd0\u884c\u65f6\u73af\u5883\u4e2d\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\u3002<\/p>\n<\/p>\n<ol>\n<li><code>None<\/code> \u662f\u5982\u4f55\u5b9e\u73b0\u7684<\/li>\n<\/ol>\n<p><p>\u5728Python\u4e2d\uff0c<code>None<\/code> \u662f\u4e00\u4e2a\u5185\u5efa\u7684\u5e38\u91cf\u5bf9\u8c61\uff0c\u5b83\u5728 Python \u7684 C \u5b9e\u73b0\u4e2d\u662f\u4e00\u4e2a <code>PyNoneObject<\/code> \u5bf9\u8c61\u3002\u8fd9\u786e\u4fdd\u4e86\u65e0\u8bba\u4f55\u65f6\u4f7f\u7528 <code>None<\/code>\uff0c\u90fd\u6307\u5411\u540c\u4e00\u4e2a\u5bf9\u8c61\u3002\u8fd9\u79cd\u8bbe\u8ba1\u4f7f\u5f97\u68c0\u67e5\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u662f <code>None<\/code> \u975e\u5e38\u9ad8\u6548\u3002<\/p>\n<\/p>\n<ol start=\"2\">\n<li><code>None<\/code> \u7684\u7279\u6027<\/li>\n<\/ol>\n<ul>\n<li>\n<p><strong>\u5355\u4f8b\u6a21\u5f0f<\/strong>\uff1a <code>None<\/code> \u662f Python \u4e2d\u7684\u5355\u4f8b\uff0c\u8fd9\u610f\u5473\u7740\u5728 Python \u7684\u6574\u4e2a\u8fd0\u884c\u65f6\u73af\u5883\u4e2d\u53ea\u6709\u4e00\u4e2a <code>None<\/code> \u5bf9\u8c61\u5b9e\u4f8b\u3002\u8fd9\u786e\u4fdd\u4e86 <code>None<\/code> \u7684\u4f7f\u7528\u4e0d\u4f1a\u5e26\u6765\u989d\u5916\u7684\u5185\u5b58\u6d88\u8017\u3002<\/p>\n<\/p>\n<\/li>\n<li>\n<p><strong>\u4e0d\u53ef\u53d8<\/strong>\uff1a <code>None<\/code> \u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u8fd9\u610f\u5473\u7740\u5b83\u7684\u503c\u4e0d\u80fd\u88ab\u66f4\u6539\u3002\u8fd9\u4f7f\u5f97 <code>None<\/code> \u53ef\u4ee5\u5b89\u5168\u5730\u7528\u4e8e\u8868\u793a\u7a7a\u503c\u800c\u4e0d\u5fc5\u62c5\u5fc3\u610f\u5916\u7684\u4fee\u6539\u3002<\/p>\n<\/p>\n<\/li>\n<li>\n<p><strong>\u5e03\u5c14\u503c<\/strong>\uff1a \u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\uff0c<code>None<\/code> \u88ab\u89c6\u4e3a <code>False<\/code>\u3002\u8fd9\u610f\u5473\u7740\u5728\u6761\u4ef6\u5224\u65ad\u4e2d\uff0c<code>None<\/code> \u4f1a\u88ab\u89c6\u4e3a\u5426\u5b9a\u3002<\/p>\n<\/p>\n<\/li>\n<\/ul>\n<p><p>\u4e8c\u3001<code>None<\/code> \u7684\u5e38\u89c1\u7528\u9014<\/p>\n<\/p>\n<ol>\n<li>\u521d\u59cb\u5316\u53d8\u91cf<\/li>\n<\/ol>\n<p><p>\u5728\u7f16\u5199\u4ee3\u7801\u65f6\uff0c\u901a\u5e38\u4f1a\u9047\u5230\u9700\u8981\u63d0\u524d\u58f0\u660e\u53d8\u91cf\u4f46\u6682\u65f6\u6ca1\u6709\u5408\u9002\u7684\u503c\u6765\u521d\u59cb\u5316\u7684\u60c5\u51b5\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c<code>None<\/code> \u662f\u4e00\u4e2a\u826f\u597d\u7684\u9009\u62e9\u3002\u4f8b\u5982\uff1a<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">result = None<\/p>\n<h2><strong>\u8fdb\u884c\u4e00\u4e9b\u64cd\u4f5c\u540e\u4e3a result \u8d4b\u503c<\/strong><\/h2>\n<p>if some_condition:<\/p>\n<p>    result = compute_result()<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"2\">\n<li>\u51fd\u6570\u7684\u9ed8\u8ba4\u8fd4\u56de\u503c<\/li>\n<\/ol>\n<p><p>\u5982\u679c\u51fd\u6570\u6ca1\u6709\u663e\u5f0f\u8fd4\u56de\u503c\uff0cPython \u4f1a\u9ed8\u8ba4\u8fd4\u56de <code>None<\/code>\u3002\u8fd9\u5728\u51fd\u6570\u53ea\u8fdb\u884c\u64cd\u4f5c\u800c\u4e0d\u9700\u8981\u8fd4\u56de\u4efb\u4f55\u7ed3\u679c\u65f6\u5f88\u6709\u7528\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">def do_something():<\/p>\n<p>    print(&quot;This function does not return anything.&quot;)<\/p>\n<p>result = do_something()  # result \u662f None<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"3\">\n<li>\u4f5c\u4e3a\u51fd\u6570\u7684\u9ed8\u8ba4\u53c2\u6570<\/li>\n<\/ol>\n<p><p>\u5728\u5b9a\u4e49\u51fd\u6570\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>None<\/code> \u4f5c\u4e3a\u9ed8\u8ba4\u53c2\u6570\u3002\u8fd9\u5728\u4f60\u5e0c\u671b\u53c2\u6570\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\u662f\u53ef\u9009\u7684\u65f6\u975e\u5e38\u6709\u7528\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">def connect_to_database(host, port, user=None, password=None):<\/p>\n<p>    # \u5982\u679c user \u548c password \u6ca1\u6709\u63d0\u4f9b\uff0c\u5c06\u4f7f\u7528\u9ed8\u8ba4\u7684\u51ed\u636e<\/p>\n<p>    if user is None:<\/p>\n<p>        user = &quot;default_user&quot;<\/p>\n<p>    if password is None:<\/p>\n<p>        password = &quot;default_password&quot;<\/p>\n<p>    # \u8fde\u63a5\u5230\u6570\u636e\u5e93\u7684\u903b\u8f91<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u4e09\u3001<code>None<\/code> \u4e0e\u5176\u4ed6\u7a7a\u503c\u7684\u6bd4\u8f83<\/p>\n<\/p>\n<p><p>Python \u4e2d\u6709\u591a\u79cd\u8868\u793a\u201c\u7a7a\u201d\u7684\u65b9\u6cd5\uff0c<code>None<\/code> \u662f\u5176\u4e2d\u4e4b\u4e00\u3002\u4e0e\u5176\u4ed6\u7a7a\u503c\uff08\u5982\u7a7a\u5b57\u7b26\u4e32 <code>&quot;&quot;<\/code>\u3001\u7a7a\u5217\u8868 <code>[]<\/code>\u3001\u7a7a\u5b57\u5178 <code>{}<\/code>\uff09\u76f8\u6bd4\uff0c<code>None<\/code> \u6709\u5176\u72ec\u7279\u7684\u7528\u9014\u548c\u7279\u6027\u3002<\/p>\n<\/p>\n<ol>\n<li><code>None<\/code> \u4e0e <code>False<\/code><\/li>\n<\/ol>\n<p><p>\u5c3d\u7ba1 <code>None<\/code> \u5728\u5e03\u5c14\u4e0a\u4e0b\u6587\u4e2d\u88ab\u89c6\u4e3a <code>False<\/code>\uff0c\u4f46\u5b83\u4e0e <code>False<\/code> \u672c\u8eab\u662f\u4e0d\u540c\u7684\u3002\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c<code>None<\/code> \u4e0d\u80fd\u4e0e <code>False<\/code> \u8fdb\u884c\u76f4\u63a5\u6bd4\u8f83\u6765\u5224\u65ad\u7a7a\u503c\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">if some_value is None:<\/p>\n<p>    # \u8fd9\u662f\u63a8\u8350\u7684\u5224\u65ad\u65b9\u5f0f<\/p>\n<p>    print(&quot;Value is None&quot;)<\/p>\n<p>if some_value == False:<\/p>\n<p>    # \u8fd9\u662f\u4e0d\u63a8\u8350\u7684\uff0c\u56e0\u4e3a\u53ef\u80fd\u4f1a\u5bfc\u81f4\u8bef\u5224<\/p>\n<p>    print(&quot;Value is False&quot;)<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"2\">\n<li><code>None<\/code> \u4e0e\u7a7a\u5b57\u7b26\u4e32<\/li>\n<\/ol>\n<p><p>\u7a7a\u5b57\u7b26\u4e32 <code>&quot;&quot;<\/code> \u662f\u4e00\u4e2a\u6709\u6548\u7684\u5b57\u7b26\u4e32\u5bf9\u8c61\uff0c\u800c <code>None<\/code> \u5219\u8868\u793a\u6ca1\u6709\u503c\u3002\u5728\u8bb8\u591a\u60c5\u51b5\u4e0b\uff0c\u4f7f\u7528\u7a7a\u5b57\u7b26\u4e32\u548c <code>None<\/code> \u662f\u4e0d\u53ef\u4ee5\u4e92\u6362\u7684\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">name = &quot;&quot;<\/p>\n<p>if name is None:<\/p>\n<p>    # \u8fd9\u4e0d\u4f1a\u6267\u884c\uff0c\u56e0\u4e3a name \u662f\u4e00\u4e2a\u7a7a\u5b57\u7b26\u4e32\uff0c\u800c\u4e0d\u662f None<\/p>\n<p>    print(&quot;Name is None&quot;)<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"3\">\n<li><code>None<\/code> \u4e0e\u7a7a\u5217\u8868<\/li>\n<\/ol>\n<p><p>\u7a7a\u5217\u8868 <code>[]<\/code> \u662f\u4e00\u4e2a\u6709\u6548\u7684\u5217\u8868\u5bf9\u8c61\uff0c\u8868\u793a\u5217\u8868\u4e2d\u6ca1\u6709\u5143\u7d20\u3002\u800c <code>None<\/code> \u8868\u793a\u6ca1\u6709\u503c\u6216\u6ca1\u6709\u5bf9\u8c61\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">items = []<\/p>\n<p>if items is None:<\/p>\n<p>    # \u8fd9\u4e0d\u4f1a\u6267\u884c\uff0c\u56e0\u4e3a items \u662f\u4e00\u4e2a\u7a7a\u5217\u8868\uff0c\u800c\u4e0d\u662f None<\/p>\n<p>    print(&quot;Items is None&quot;)<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u56db\u3001\u5904\u7406 <code>None<\/code> \u7684\u6700\u4f73\u5b9e\u8df5<\/p>\n<\/p>\n<ol>\n<li>\u4f7f\u7528 <code>is<\/code> \u548c <code>is not<\/code> \u8fdb\u884c\u6bd4\u8f83<\/li>\n<\/ol>\n<p><p>\u5f53\u9700\u8981\u68c0\u67e5\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3a <code>None<\/code> \u65f6\uff0c\u4f7f\u7528 <code>is<\/code> \u6216 <code>is not<\/code> \u662f\u6700\u597d\u7684\u9009\u62e9\u3002\u8fd9\u662f\u56e0\u4e3a <code>None<\/code> \u662f\u4e00\u4e2a\u5355\u4f8b\u5bf9\u8c61\uff0c\u4f7f\u7528 <code>is<\/code> \u53ef\u4ee5\u786e\u4fdd\u6bd4\u8f83\u7684\u662f\u5bf9\u8c61\u7684\u8eab\u4efd\u800c\u4e0d\u662f\u503c\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">if some_variable is None:<\/p>\n<p>    print(&quot;Variable is None&quot;)<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"2\">\n<li>\u907f\u514d\u5bf9 <code>None<\/code> \u8fdb\u884c\u4e0d\u5fc5\u8981\u7684\u64cd\u4f5c<\/li>\n<\/ol>\n<p><p>\u7531\u4e8e <code>None<\/code> \u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u5bf9\u8c61\uff0c\u5728\u5bf9\u5176\u8fdb\u884c\u64cd\u4f5c\u65f6\u5e94\u5c0f\u5fc3\u3002\u4f8b\u5982\uff0c\u4e0d\u8981\u5bf9 <code>None<\/code> \u8c03\u7528\u65b9\u6cd5\u6216\u8fdb\u884c\u8fd0\u7b97\uff0c\u56e0\u4e3a\u8fd9\u4f1a\u5bfc\u81f4\u5f02\u5e38\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">some_variable = None<\/p>\n<h2><strong>\u4ee5\u4e0b\u64cd\u4f5c\u4f1a\u5bfc\u81f4\u5f02\u5e38<\/strong><\/h2>\n<h2><strong>some_variable.append(1)<\/strong><\/h2>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"3\">\n<li>\u5728\u6587\u6863\u4e2d\u660e\u786e\u6307\u51fa <code>None<\/code> \u7684\u4f7f\u7528<\/li>\n<\/ol>\n<p><p>\u5728\u7f16\u5199\u4ee3\u7801\u65f6\uff0c\u5c24\u5176\u662f\u5e93\u6216\u6846\u67b6\uff0c\u5e94\u8be5\u5728\u6587\u6863\u4e2d\u660e\u786e\u6307\u51fa\u4f55\u65f6\u4f1a\u8fd4\u56de\u6216\u63a5\u53d7 <code>None<\/code>\u3002\u8fd9\u6709\u52a9\u4e8e\u4f7f\u7528\u8005\u6b63\u786e\u7406\u89e3\u548c\u4f7f\u7528\u4ee3\u7801\u3002<\/p>\n<\/p>\n<p><p>\u4e94\u3001<code>None<\/code> \u5728\u6570\u636e\u5904\u7406\u4e2d\u7684\u5e94\u7528<\/p>\n<\/p>\n<ol>\n<li>\u6570\u636e\u6e05\u7406\u548c\u9884\u5904\u7406<\/li>\n<\/ol>\n<p><p>\u5728\u6570\u636e\u5904\u7406\u8fc7\u7a0b\u4e2d\uff0c<code>None<\/code> \u53ef\u4ee5\u7528\u6765\u8868\u793a\u7f3a\u5931\u503c\u6216\u65e0\u6548\u6570\u636e\u3002\u8bb8\u591a\u6570\u636e\u5904\u7406\u5e93\uff08\u5982 Pandas\uff09\u5728\u5904\u7406\u7f3a\u5931\u6570\u636e\u65f6\u4f1a\u4f7f\u7528 <code>None<\/code> \u6216 <code>NaN<\/code>\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">import pandas as pd<\/p>\n<p>data = {&#39;Name&#39;: [&#39;Alice&#39;, &#39;Bob&#39;, None], &#39;Age&#39;: [24, None, 30]}<\/p>\n<p>df = pd.DataFrame(data)<\/p>\n<p>print(df)<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"2\">\n<li>\u6570\u636e\u5e93\u64cd\u4f5c<\/li>\n<\/ol>\n<p><p>\u5728\u6570\u636e\u5e93\u64cd\u4f5c\u4e2d\uff0c<code>None<\/code> \u901a\u5e38\u7528\u4e8e\u8868\u793a NULL \u503c\u3002\u5728\u4e0e\u6570\u636e\u5e93\u4ea4\u4e92\u65f6\uff0cPython \u4e2d\u7684 <code>None<\/code> \u53ef\u4ee5\u81ea\u52a8\u6620\u5c04\u5230 SQL \u4e2d\u7684 NULL\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">import sqlite3<\/p>\n<p>conn = sqlite3.connect(&#39;example.db&#39;)<\/p>\n<p>cursor = conn.cursor()<\/p>\n<p>cursor.execute(&#39;INSERT INTO users (name, age) VALUES (?, ?)&#39;, (None, 25))<\/p>\n<p>conn.commit()<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u516d\u3001<code>None<\/code> \u7684\u6f5c\u5728\u95ee\u9898\u53ca\u5176\u89e3\u51b3<\/p>\n<\/p>\n<ol>\n<li><code>None<\/code> \u5f15\u53d1\u7684\u5f02\u5e38<\/li>\n<\/ol>\n<p><p>\u5728\u4f7f\u7528 <code>None<\/code> \u65f6\uff0c\u5982\u679c\u4e0d\u5c0f\u5fc3\u5bf9\u5176\u6267\u884c\u4e86\u4e0d\u5f53\u64cd\u4f5c\uff0c\u53ef\u80fd\u4f1a\u5f15\u53d1 <code>AttributeError<\/code> \u6216 <code>TypeError<\/code>\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">some_variable = None<\/p>\n<h2><strong>\u4ee5\u4e0b\u64cd\u4f5c\u4f1a\u5f15\u53d1\u5f02\u5e38<\/strong><\/h2>\n<h2><strong>some_variable.upper()<\/strong><\/h2>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u4e3a\u907f\u514d\u8fd9\u4e9b\u95ee\u9898\uff0c\u53ef\u4ee5\u5728\u64cd\u4f5c\u524d\u6dfb\u52a0\u68c0\u67e5\uff1a<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">if some_variable is not None:<\/p>\n<p>    some_variable.upper()<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"2\">\n<li><code>None<\/code> \u4e0e\u9ed8\u8ba4\u53c2\u6570\u7684\u9677\u9631<\/li>\n<\/ol>\n<p><p>\u5728\u4f7f\u7528\u53ef\u53d8\u5bf9\u8c61\u4f5c\u4e3a\u9ed8\u8ba4\u53c2\u6570\u65f6\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u610f\u60f3\u4e0d\u5230\u7684\u7ed3\u679c\u3002\u4e3a\u4e86\u907f\u514d\u8fd9\u4e2a\u95ee\u9898\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>None<\/code> \u5e76\u5728\u51fd\u6570\u5185\u90e8\u8fdb\u884c\u5904\u7406\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">def append_to_list(value, my_list=None):<\/p>\n<p>    if my_list is None:<\/p>\n<p>        my_list = []<\/p>\n<p>    my_list.append(value)<\/p>\n<p>    return my_list<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u4e03\u3001<code>None<\/code> \u4e0e\u9762\u5411\u5bf9\u8c61\u7f16\u7a0b<\/p>\n<\/p>\n<ol>\n<li>\u7c7b\u4e2d\u7684 <code>None<\/code> \u7528\u6cd5<\/li>\n<\/ol>\n<p><p>\u5728\u9762\u5411\u5bf9\u8c61\u7f16\u7a0b\u4e2d\uff0c<code>None<\/code> \u53ef\u4ee5\u7528\u6765\u521d\u59cb\u5316\u5bf9\u8c61\u7684\u5c5e\u6027\uff0c\u5c24\u5176\u662f\u5728\u5c5e\u6027\u7684\u503c\u9700\u8981\u7a0d\u540e\u786e\u5b9a\u7684\u60c5\u51b5\u4e0b\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">class Example:<\/p>\n<p>    def __init__(self):<\/p>\n<p>        self.value = None<\/p>\n<p><\/code><\/pre>\n<\/p>\n<ol start=\"2\">\n<li>\u65b9\u6cd5\u8fd4\u56de <code>None<\/code><\/li>\n<\/ol>\n<p><p>\u5728\u5b9a\u4e49\u7c7b\u7684\u65b9\u6cd5\u65f6\uff0c\u53ef\u4ee5\u8bbe\u8ba1\u4e00\u4e9b\u65b9\u6cd5\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\u8fd4\u56de <code>None<\/code>\uff0c\u4ee5\u8868\u793a\u64cd\u4f5c\u5931\u8d25\u6216\u672a\u627e\u5230\u7ed3\u679c\u3002<\/p>\n<\/p>\n<p><pre><code class=\"language-python\">class Cont<a href=\"https:\/\/docs.pingcode.com\/blog\/59162.html\" target=\"_blank\">AI<\/a>ner:<\/p>\n<p>    def __init__(self):<\/p>\n<p>        self.items = []<\/p>\n<p>    def find_item(self, item):<\/p>\n<p>        if item in self.items:<\/p>\n<p>            return item<\/p>\n<p>        return None<\/p>\n<p><\/code><\/pre>\n<\/p>\n<p><p>\u901a\u8fc7\u4ee5\u4e0a\u5bf9 <code>None<\/code> \u7684\u6df1\u5165\u63a2\u8ba8\uff0c\u53ef\u4ee5\u66f4\u597d\u5730\u7406\u89e3\u5176\u5728 Python \u7f16\u7a0b\u4e2d\u7684\u91cd\u8981\u6027\u548c\u5e94\u7528\u573a\u666f\u3002\u719f\u7ec3\u638c\u63e1 <code>None<\/code> \u7684\u4f7f\u7528\u80fd\u591f\u63d0\u5347\u4ee3\u7801\u7684\u5065\u58ee\u6027\u548c\u53ef\u8bfb\u6027\u3002<\/p>\n<\/p>\n<h2><strong>\u76f8\u5173\u95ee\u7b54FAQs\uff1a<\/strong><\/h2>\n<p> <strong>\u5728Python\u4e2d\uff0c\u5982\u4f55\u5224\u65ad\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3a\u7a7a\u503c\uff1f<\/strong><br \/>\u5728Python\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>if<\/code> \u8bed\u53e5\u6765\u5224\u65ad\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3a\u7a7a\u503c\u3002\u5e38\u7528\u7684\u65b9\u6cd5\u662f\u76f4\u63a5\u4f7f\u7528 <code>if not variable:<\/code> \u7ed3\u6784\u3002\u8fd9\u5c06\u68c0\u67e5\u53d8\u91cf\u662f\u5426\u4e3a <code>None<\/code>\u3001\u7a7a\u5b57\u7b26\u4e32\u3001\u7a7a\u5217\u8868\u3001\u7a7a\u5b57\u5178\u6216\u5176\u4ed6\u88ab\u8ba4\u4e3a\u662f\u201c\u7a7a\u201d\u7684\u503c\u3002\u5982\u679c\u9700\u8981\u66f4\u5177\u4f53\u7684\u68c0\u67e5\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>is None<\/code> \u6765\u5224\u65ad\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u786e\u5b9e\u662f <code>None<\/code>\u3002<\/p>\n<p><strong>\u7a7a\u503c\u5728Python\u4e2d\u4e0e\u5176\u4ed6\u7f16\u7a0b\u8bed\u8a00\u4e2d\u7684\u8868\u793a\u65b9\u5f0f\u6709\u4f55\u4e0d\u540c\uff1f<\/strong><br \/>\u5728Python\u4e2d\uff0c\u7a7a\u503c\u901a\u5e38\u4f7f\u7528 <code>None<\/code> \u6765\u8868\u793a\uff0c\u8fd9\u4e0e\u8bb8\u591a\u5176\u4ed6\u7f16\u7a0b\u8bed\u8a00\uff08\u5982Java\u4e2d\u7684<code>null<\/code>\u6216JavaScript\u4e2d\u7684<code>undefined<\/code>\uff09\u6709\u6240\u4e0d\u540c\u3002<code>None<\/code> \u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u5bf9\u8c61\uff0c\u8868\u793a\u201c\u6ca1\u6709\u503c\u201d\u6216\u201c\u7a7a\u503c\u201d\u3002\u6b64\u5916\uff0cPython\u4e2d\u8fd8\u6709\u4e00\u4e9b\u5176\u4ed6\u7684\u201c\u5047\u503c\u201d\uff0c\u5982\u7a7a\u5b57\u7b26\u4e32<code>&quot;&quot;<\/code>\u3001\u7a7a\u5217\u8868<code>[]<\/code>\u548c\u7a7a\u5b57\u5178<code>{}<\/code>\uff0c\u8fd9\u4e9b\u4e5f\u4f1a\u88ab\u89c6\u4e3a\u5e03\u5c14\u503c <code>False<\/code>\u3002<\/p>\n<p><strong>\u5982\u4f55\u5728Python\u4e2d\u4f7f\u7528\u7a7a\u503c\uff1f<\/strong><br \/>\u5728Python\u4e2d\uff0c\u7a7a\u503c\uff08None\uff09\u53ef\u4ee5\u7528\u4f5c\u51fd\u6570\u7684\u9ed8\u8ba4\u53c2\u6570\u3001\u8868\u793a\u7f3a\u5931\u7684\u6570\u636e\u6216\u5728\u6570\u636e\u7ed3\u6784\u4e2d\u5360\u4f4d\u3002\u4f8b\u5982\uff0c\u53ef\u4ee5\u5728\u51fd\u6570\u5b9a\u4e49\u4e2d\u5c06\u53c2\u6570\u8bbe\u4e3a <code>None<\/code>\uff0c\u4ee5\u4fbf\u5728\u672a\u63d0\u4f9b\u5177\u4f53\u503c\u65f6\u4f7f\u7528\u9ed8\u8ba4\u884c\u4e3a\u3002\u5728\u6570\u636e\u5904\u7406\u4e2d\uff0c\u5e38\u5e38\u4f7f\u7528 <code>None<\/code> \u6765\u8868\u793a\u7f3a\u5931\u7684\u6570\u636e\uff0c\u4f7f\u5f97\u7a0b\u5e8f\u53ef\u4ee5\u6709\u6548\u5730\u5904\u7406\u548c\u68c0\u67e5\u8fd9\u4e9b\u7a7a\u503c\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"\u5728Python\u4e2d\uff0c\u7a7a\u503c\u901a\u5e38\u4f7f\u7528None\u8868\u793a\u3001None\u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u5e38\u91cf\u3001\u7528\u6765\u8868\u793a\u7a7a\u3001\u6216\u6ca1\u6709\u503c\u7684\u72b6\u6001\u3001\u5728\u53d8\u91cf\u58f0\u660e\u3001 [&hellip;]","protected":false},"author":3,"featured_media":1004233,"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\/1004222"}],"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=1004222"}],"version-history":[{"count":"1","href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/1004222\/revisions"}],"predecessor-version":[{"id":1004235,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/1004222\/revisions\/1004235"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media\/1004233"}],"wp:attachment":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media?parent=1004222"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/categories?post=1004222"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/tags?post=1004222"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}