{"id":612,"date":"2021-01-07T17:25:31","date_gmt":"2021-01-07T09:25:31","guid":{"rendered":"http:\/\/blog.refusea.com\/?p=612"},"modified":"2021-01-14T11:06:36","modified_gmt":"2021-01-14T03:06:36","slug":"python-%e7%9a%84%e9%80%bb%e8%be%91%e8%bf%90%e7%ae%97","status":"publish","type":"post","link":"https:\/\/refusea.com\/?p=612","title":{"rendered":"Java \u7a0b\u5e8f\u5458\u5b66 python\uff1a\u903b\u8f91\u503c\u53ca\u5176\u8fd0\u7b97"},"content":{"rendered":"<h2>\u6982\u8ff0<\/h2>\n<p>bool \u662f python \u5185\u5efa\u6570\u636e\u7c7b\u578b\uff0c\u5176\u53d6\u503c\u53ea\u6709 <code>True<\/code> \u548c <code>False<\/code>\uff1bpython \u7684\u903b\u8f91\u8fd0\u7b97\u7b26\u6709 <code>not<\/code>\uff0c<code>and<\/code>\uff0c<code>or<\/code><\/p>\n<p>\u770b\u4e0a\u53bb\u5f88\u7b80\u5355\uff0c\u6240\u4ee5\u5f53\u6211\u7b2c\u4e00\u6b21\u770b\u5230\u4e0b\u9762\u7684\u4ee3\u7801\u65f6\u6211\u662f\u61f5\u903c\u7684<\/p>\n<pre><code class=\"language-python\">id = item.get(&#039;id&#039;) or &#039;&#039;<\/code><\/pre>\n<p>\u4f5c\u4e3a\u4e00\u4e2a\u4e3b\u8981\u4f7f\u7528 Java \u7684\u7a0b\u5e8f\u5458\u6765\u8bf4\uff0c\u53ea\u6709\u903b\u8f91\u7c7b\u578b\u7684\u53d8\u91cf\u624d\u53ef\u4ee5\u4f7f\u7528\u903b\u8f91\u8fd0\u7b97\u7b26\uff0c\u5df2\u7ecf\u6210\u4e86\u601d\u7ef4\u5b9a\u5f0f\uff0c\u5bf9\u4e8e python\uff0c\u8fd9\u4e9b\u601d\u7ef4\u5b9a\u5f0f\u53cd\u800c\u6210\u4e86\u969c\u788d<\/p>\n<h2>python \u903b\u8f91\u5224\u65ad<\/h2>\n<p>python \u7684\u6240\u6709\u53d8\u91cf\u90fd\u53ef\u4ee5\u8fdb\u884c\u903b\u8f91\u6bd4\u8f83\uff0c\u5176\u4e2d\uff0c\u5982\u4e0b\u53d8\u91cf\u7684 bool \u503c\u603b\u662f <code>False<\/code><\/p>\n<pre><code class=\"language-python\">0, 0.0, [], {}, (), &quot;&quot;, &#039;&#039;, None, False<\/code><\/pre>\n<p>\u5982\u4f55\u7406\u89e3\u8fd9\u4e2a\u7ed3\u8bba\u5462\uff1f<\/p>\n<ul>\n<li><code>None<\/code>\uff1a\u603b\u662f <code>False<\/code>\uff0c\u8fd9\u662f python \u8bed\u8a00\u7279\u6027<\/li>\n<li>\u6570\u503c\uff1a\u5bf9\u4e8e\u6570\u503c n\uff0c\u5982\u679c <code>n==0<\/code>\uff0c\u90a3\u4e48 n \u7684 bool \u503c\u5c31\u662f <code>False<\/code>\uff0c\u53cd\u4e4b\u4e3a <code>True<\/code><\/li>\n<li>\u5bf9\u4e8e\u96c6\u5408\/\u5b57\u7b26\u4e32\/\u6216\u5176\u4ed6\u7c7b\u578b x\uff0c\u5982\u679c <code>len(x)==0<\/code>\uff0c\u90a3\u4e48 x \u7684 bool \u503c\u5c31\u662f <code>False<\/code>\uff0c\u53cd\u4e4b\u4e3a <code>True<\/code><\/li>\n<li>\u5bf9\u4e8e\u65b9\u6cd5\uff0c\u5176 bool \u503c\u603b\u662f <code>True<\/code>\uff0c\u6240\u4ee5\u4e00\u5b9a\u8981\u6ce8\u610f\uff0c\u5728\u903b\u8f91\u8868\u8fbe\u5f0f\u91cc\u4e0d\u8981\u5ffd\u7565\u4e86\u65b9\u6cd5\u7684\u62ec\u53f7<\/li>\n<li>\u81ea\u5b9a\u4e49\u7684\u7c7b\uff0c\u5176\u5b9e\u4f8b\u5bf9\u8c61\u7684 bool \u503c\u603b\u662f <code>True<\/code>\uff0c\u5982\u679c\u60f3\u8981\u6539\u53d8\uff0c\u53ef\u4ee5\u5b9e\u73b0\u5982\u4e0b\u65b9\u6cd5\n<ul>\n<li><code>__bool__()<\/code><\/li>\n<li><code>__len__()<\/code><\/li>\n<li>\u5982\u679c\u540c\u65f6\u5b58\u5728 <code>__bool__()<\/code>\uff0c<code>__len__()<\/code>\uff0c\u5219 <code>__bool()__<\/code> \u4f18\u5148<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>python \u7684 or \u548c and \u8fd0\u7b97\u7b26<\/h2>\n<p>\u56de\u5230\u672c\u6587\u7684\u5f00\u5934\uff0c\u6765\u770b\u4e0b <code>or<\/code> \u8fd0\u7b97\u7b26<\/p>\n<p>\u9996\u5148\u8981\u660e\u786e\u4e00\u70b9\uff1apython \u7684 <code>or<\/code> \u5e76\u4e0d\u4fdd\u8bc1\u53ea\u8fd4\u56de bool \u503c\uff0c\u5373 <code>True<\/code> \u6216 <code>False<\/code><\/p>\n<p><code>or<\/code> \u8fd0\u7b97\u6709\u4e2a\u77ed\u8def\u7279\u6027\uff0c\u5373\u9047\u5230\u7b2c\u4e00\u4e2a <code>True<\/code> \u65f6\u5c31\u53ef\u4ee5\u8fd4\u56de\uff0c\u4e0d\u9700\u8981\u8ba1\u7b97\u540e\u7eed\u7684\u8868\u8fbe\u5f0f\uff0c\u800c\u4e14\u5b83\u8fd4\u56de\u7684\u662f\u7b2c\u4e00\u4e2a\u4e3a <code>True<\/code> \u7684\u53d8\u91cf\uff0c\u5e76\u4e0d\u4e00\u5b9a\u662f <code>True<\/code>\uff0c\u6bd4\u5982\u8bf4 <code>1<\/code> \u4e5f\u662f True\uff0c\u90a3\u4e48\u8fd4\u56de\u7684\u5c31\u662f <code>1<\/code>\uff0c\u793a\u4f8b\u5982\u4e0b<\/p>\n<pre><code class=\"language-python\">>&gt;&gt; 0 or 1 or None or True\n1<\/code><\/pre>\n<p>\u5982\u679c <code>or<\/code> \u6ca1\u6709\u53d1\u751f\u77ed\u8def\uff0c\u5373\u8ba1\u7b97\u5230\u6700\u540e\u4e00\u4e2a\u503c\u8fd8\u662f\u6ca1\u6709\u9047\u5230 <code>True<\/code>\uff0c\u90a3\u4e48\u4f1a\u8fd4\u56de\u8fd9\u6700\u540e\u7684\u4e00\u4e2a\u503c\uff0c\u6240\u4ee5\u672c\u6587\u6700\u521d\u7684\u4ee3\u7801\uff0c\u5176\u542b\u4e49\u5982\u4e0b<\/p>\n<pre><code class=\"language-python\"># \u5982\u679c item.id \u662f None\uff0c\u5219 id \u503c\u4e3a &#039;&#039;\nid = item.get(&#039;id&#039;) or &#039;&#039;<\/code><\/pre>\n<p>\u8fd9\u76f8\u5f53\u4e8e\u7ed9 id \u4e00\u4e2a\u9ed8\u8ba4\u503c <code>&#039;&#039;<\/code> \u6765\u907f\u514d\u5176\u503c\u4e3a <code>None<\/code>\uff0c\u56e0\u4e3a\u5bf9\u5e94\u7684\u6570\u636e\u5e93\u5b57\u6bb5\u53ef\u80fd\u4e0d\u5141\u8bb8\u4e3a <code>null<\/code><\/p>\n<p>\u540c\u6837\u7684\uff0c<code>and<\/code> \u4e5f\u6709\u77ed\u8def\u7279\u6027\uff0c\u5b83\u9047\u5230\u7b2c\u4e00\u4e2a <code>False<\/code> \u5c31\u53ef\u4ee5\u8fd4\u56de\u5bf9\u5e94\u7684\u53d8\u91cf\uff0c\u6216\u8005\u8fd4\u56de\u6700\u540e\u4e00\u4e2a\u53d8\u91cf\uff0c\u793a\u4f8b\u5982\u4e0b<\/p>\n<pre><code class=\"language-python\">>&gt;&gt; 1 and {&#039;x&#039;:1} and [] and True\n[]\n\n>&gt;&gt; 1 and True and [1,2] and [3,4]\n[3, 4]<\/code><\/pre>\n<h2>python \u7684 not<\/h2>\n<p><code>not<\/code> \u5c31\u6bd4\u8f83\u7279\u6b8a\u4e86\uff0c\u5b83\u8fd4\u56de\u7684\u662f bool \u503c\uff0c\u5373 <code>True<\/code> \u6216 <code>False<\/code>\uff0c\u793a\u4f8b\u5982\u4e0b<\/p>\n<pre><code class=\"language-python\">>&gt;&gt; not None\nTrue\n>&gt;&gt; not 100\nFalse\n>&gt;&gt; not [1]\nFalse\n>&gt;&gt; not {}\nTrue<\/code><\/pre>\n<h2>python \u65b9\u6cd5\u53c2\u4e0e\u903b\u8f91\u8fd0\u7b97<\/h2>\n<p>python \u7684\u65b9\u6cd5\u672c\u8eab\u4e5f\u662f\u5bf9\u8c61\uff0c\u53ef\u4ee5\u8d4b\u503c\u7ed9\u53d8\u91cf<\/p>\n<p>\u524d\u9762\u5df2\u7ecf\u8bf4\u4e86\uff0c\u65b9\u6cd5\u7684 bool \u503c\u603b\u662f <code>True<\/code>\uff0c\u6240\u4ee5\u8981\u5c0f\u5fc3\uff0c\u5fd8\u8bb0\u7ed9\u65b9\u6cd5\u5199\u4e0a\u62ec\u53f7\u662f\u4f1a\u5bfc\u81f4\u5947\u602a\u7684\u95ee\u9898\u7684\uff0c\u6392\u67e5\u8d77\u6765\u5f88\u75db\u82e6\uff0c\u793a\u4f8b\u5982\u4e0b<\/p>\n<pre><code class=\"language-python\"># \u5b9a\u4e49\u4e00\u4e2a\u65b9\u6cd5\uff0c\u603b\u662f\u8fd4\u56de False\n>&gt;&gt; def always_false():\n...   return False\n\n# \u9884\u671f\u6253\u5370\u51fa bad\n>&gt;&gt; x = always_false()\n>&gt;&gt; if x:\n...   print(&#039;ok&#039;)\n... else:\n...   print(&#039;bad&#039;)\n...\nbad\n\n# \u4e0d\u614e\u6ca1\u6709\u5199\u65b9\u6cd5\u540e\u7684\u62ec\u53f7\uff0c\u5bfc\u81f4\u8fd0\u884c\u9519\u8bef\n>&gt;&gt; x = always_false\n>&gt;&gt; if x:\n...   print(&#039;ok&#039;)\n... else:\n...   print(&#039;bad&#039;)\n...\nok\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>\u6982\u8ff0 bool \u662f python \u5185\u5efa\u6570\u636e\u7c7b\u578b\uff0c\u5176\u53d6\u503c\u53ea\u6709 True \u548c False\uff1bpython \u7684\u903b\u8f91\u8fd0\u7b97 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[38],"tags":[],"class_list":["post-612","post","type-post","status-publish","format-standard","hentry","category-python"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ 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