{"id":207215,"date":"2020-11-25T04:53:02","date_gmt":"2020-11-24T20:53:02","guid":{"rendered":"http:\/\/4563.org\/?p=207215"},"modified":"2020-11-25T04:53:02","modified_gmt":"2020-11-24T20:53:02","slug":"python-%e9%ab%98%e9%98%b6-lambda-%e5%87%bd%e6%95%b0%e7%9a%84%e5%9b%9b%e7%a7%8d%e5%b8%b8%e8%a7%81%e9%94%99%e8%af%af","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=207215","title":{"rendered":"Python \u9ad8\u9636 Lambda \u51fd\u6570\u7684\u56db\u79cd\u5e38\u89c1\u9519\u8bef"},"content":{"rendered":"
\n
\n
\n

Python \u9ad8\u9636 Lambda \u51fd\u6570\u7684\u56db\u79cd\u5e38\u89c1\u9519\u8bef <\/h1>\n

<\/p>\n

\n
\u8cc7\u6df1\u5927\u4f6c : fanqieipnet <\/span> <\/i> 3<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
Lambda \u51fd\u6570\u662f Python \u4e2d\u7684\u533f\u540d\u51fd\u6570\u3002\u5f53\u4f60\u9700\u8981\u5b8c\u6210\u4e00\u4ef6\u5c0f\u5de5\u4f5c\u65f6\uff0c\u5728\u672c\u5730\u73af\u5883\u4e2d\u4f7f\u7528\u5b83\u4eec\u53ef\u4ee5\u8ba9\u5de5\u4f5c\u5f97\u5fc3\u5e94\u624b\u3002\u6709\u4e9b\u4eba\u5c06\u5b83\u4eec\u7b80\u79f0\u4e3a lambdas\uff0c\u5b83\u4eec\u7684\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n

\u3000\u3000 lambda arguments: expression<\/p>\n

\u3000\u3000 lambda \u5173\u952e\u5b57\u53ef\u4ee5\u7528\u6765\u521b\u5efa\u4e00\u4e2a lambda \u51fd\u6570\uff0c\u7d27\u8ddf\u5176\u540e\u7684\u662f\u53c2\u6570\u5217\u8868\u548c\u7528\u5192\u53f7\u5206\u5272\u5f00\u7684\u5355\u4e2a\u8868\u8fbe\u5f0f\u3002\u4f8b\u5982\uff0clambda x: 2 * x \u662f\u5c06\u4efb\u4f55\u8f93\u5165\u7684\u6570\u4e58 2\uff0c\u800c lambda x, y: x+y \u662f\u8ba1\u7b97\u4e24\u4e2a\u6570\u5b57\u7684\u548c\u3002\u8bed\u6cd5\u5341\u5206\u76f4\u622a\u4e86\u5f53\uff0c\u5bf9\u5427?<\/p>\n

\u3000\u3000\u5047\u8bbe\u60a8\u77e5\u9053\u4ec0\u4e48\u662f lambda \u51fd\u6570\uff0c\u672c\u6587\u756a\u8304\u52a0\u901f\u65e8\u5728\u63d0\u4f9b\u6709\u5173\u5982\u4f55\u6b63\u786e\u4f7f\u7528 lambda \u51fd\u6570\u7684\u4e00\u4e9b\u5e38\u89c4\u51c6\u5219\u3002<\/p>\n

\u3000\u3000 1. \u4e0d\u8981\u8fd4\u56de\u4efb\u4f55\u503c<\/p>\n

\u3000\u3000\u770b\u770b\u8bed\u6cd5\uff0c\u60a8\u53ef\u80fd\u4f1a\u6ce8\u610f\u5230\u6211\u4eec\u5728 lambda \u51fd\u6570\u4e2d\u5e76\u6ca1\u6709\u8fd4\u56de\u4efb\u4f55\u5185\u5bb9\u3002\u8fd9\u90fd\u662f\u56e0\u4e3a lambda \u51fd\u6570\u53ea\u80fd\u5305\u542b\u4e00\u4e2a\u8868\u8fbe\u5f0f\u3002\u7136\u800c\uff0c\u4f7f\u7528 return \u5173\u952e\u5b57\u4f1a\u6784\u6210\u4e0d\u7b26\u5408\u89c4\u5b9a\u8bed\u6cd5\u7684\u8bed\u53e5\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n

\u3000\u3000>>> integers = [(3, -3), (2, 3), (5, 1), (-4, 4)]<\/p>\n

\u3000\u3000>>> sorted(integers, key=lambda x: x[-1])<\/p>\n

\u3000\u3000[(3, -3), (5, 1), (2, 3), (-4, 4)]<\/p>\n

\u3000\u3000>>> sorted(integers, key=lambda x: return x[-1])<\/p>\n

\u3000\u3000…<\/p>\n

\u3000 File “<input>”, line 1<\/p>\n

\u3000\u3000 sorted(integers, key=lambda x: return x[-1])<\/p>\n

\u3000\u3000^<\/p>\n

\u3000\u3000 SyntaxError: invalid syntax<\/p>\n

\u3000\u3000\u8be5\u9519\u8bef\u53ef\u80fd\u662f\u7531\u4e8e\u65e0\u6cd5\u533a\u5206\u8868\u8fbe\u5f0f\u548c\u8bed\u53e5\u800c\u5f15\u8d77\u7684\u3002\u50cf\u662f\u5305\u542b return \u3001try \u3001with \u4ee5\u53ca if \u7684\u8bed\u53e5\u4f1a\u6267\u884c\u7279\u6b8a\u52a8\u4f5c\u3002\u7136\u800c\uff0c\u8868\u8fbe\u5f0f\u6307\u7684\u662f\u90a3\u4e9b\u53ef\u4ee5\u88ab\u8ba1\u7b97\u51fa\u4e00\u4e2a\u503c\u7684\u8868\u8fbe\uff0c\u4f8b\u5982\u6570\u503c\u6216\u5176\u4ed6 Python \u5bf9\u8c61\u3002<\/p>\n

\u3000\u3000\u901a\u8fc7\u4f7f\u7528 lambda \u51fd\u6570\uff0c\u5355\u4e2a\u8868\u8fbe\u5f0f\u4f1a\u88ab\u8ba1\u7b97\u4e3a\u4e00\u4e2a\u503c\u5e76\u4e14\u53c2\u4e0e\u540e\u7eed\u7684\u8ba1\u7b97\uff0c\u4f8b\u5982\u7531 sorted \u51fd\u6570\u6392\u5e8f\u3002<\/p>\n

\u3000\u3000 2. \u4e0d\u8981\u5fd8\u8bb0\u66f4\u597d\u7684\u9009\u62e9<\/p>\n

\u3000\u3000 lambda \u51fd\u6570\u6700\u5e38\u89c1\u7684\u4f7f\u7528\u573a\u666f\u662f\u5c06\u5b83\u4f5c\u4e3a\u4e00\u4e9b\u5185\u7f6e\u5de5\u5177\u51fd\u6570\u4e2d key \u7684\u5b9e\u53c2\uff0c\u6bd4\u5982\u4e0a\u9762\u5c55\u793a\u7684 sorted() \u548c max()\u3002\u6839\u636e\u60c5\u51b5\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5176\u4ed6\u66ff\u4ee3\u65b9\u6cd5\u3002\u601d\u8003\u4e0b\u9762\u7684\u4f8b\u5b50\uff1a<\/p>\n

\u3000\u3000>>> integers = [-4, 3, 7, -5, -2, 6]<\/p>\n

\u3000\u3000>>> sorted(integers, key=lambda x: abs(x))<\/p>\n

\u3000\u3000[-2, 3, -4, -5, 6, 7]<\/p>\n

\u3000\u3000>>> sorted(integers, key=abs)<\/p>\n

\u3000\u3000[-2, 3, -4, -5, 6, 7]<\/p>\n

\u3000\u3000>>> scores = [(93, 100), (92, 99), (95, 94)]<\/p>\n

\u3000\u3000>>> max(scores, key=lambda x: x[0] + x[1])<\/p>\n

\u3000\u3000(93, 100)<\/p>\n

\u3000\u3000>>> max(scores, key=sum)<\/p>\n

\u3000\u3000(93, 100)<\/p>\n

\u3000\u3000\u5728\u6570\u636e\u79d1\u5b66\u9886\u57df\uff0c\u5f88\u591a\u4eba\u4f7f\u7528 pandas \u5e93\u6765\u5904\u7406\u6570\u636e\u3002\u5982\u4e0b\u6240\u793a\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 lambda \u51fd\u6570\u901a\u8fc7 map() \u51fd\u6570\u4ece\u73b0\u6709\u6570\u636e\u4e2d\u521b\u5efa\u65b0\u6570\u636e\u3002\u9664\u4e86\u4f7f\u7528 lambda \u51fd\u6570\u5916\uff0c\u6211\u4eec\u8fd8\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u7b97\u672f\u51fd\u6570\uff0c\u56e0\u4e3a pandas \u662f\u652f\u6301\u7684\uff1a<\/p>\n

\u3000\u3000>>> import pandas as pd<\/p>\n

\u3000\u3000>>> data = pd.Series([1, 2, 3, 4])<\/p>\n

\u3000\u3000>>> data.map(lambda x: x + 5)<\/p>\n

\u3000\u3000 0 6<\/p>\n

\u3000\u3000 1 7<\/p>\n

\u3000\u3000 2 8<\/p>\n

\u3000\u3000 3 9<\/p>\n

\u3000\u3000 dtype: int64<\/p>\n

\u3000\u3000>>> data + 5<\/p>\n

\u3000\u3000 0 6<\/p>\n

\u3000\u3000 1 7<\/p>\n

\u3000\u3000 2 8<\/p>\n

\u3000\u3000 3 9<\/p>\n

\u3000\u3000 dtype: int64<\/p>\n

\u3000\u3000 3. \u4e0d\u8981\u5c06\u5b83\u8d4b\u503c\u7ed9\u53d8\u91cf<\/p>\n

\u3000\u3000\u6211\u66fe\u89c1\u8fc7\u4e00\u4e9b\u4eba\u5c06 lambda \u51fd\u6570\u8bef\u8ba4\u4e3a\u662f\u7b80\u5355\u51fd\u6570\u7684\u53e6\u4e00\u79cd\u58f0\u660e\u65b9\u5f0f\uff0c\u60a8\u53ef\u80fd\u4e5f\u89c1\u8fc7\u6709\u4eba\u50cf\u4e0b\u9762\u8fd9\u4e48\u505a\uff1a<\/p>\n

\u3000\u3000>>> doubler = lambda x: 2 * x<\/p>\n

\u3000\u3000>>> doubler(5)<\/p>\n

\u3000\u3000 10<\/p>\n

\u3000\u3000>>> doubler(7)<\/p>\n

\u3000\u3000 14<\/p>\n

\u3000\u3000>>> type(doubler)<\/p>\n

\u3000\u3000<\/p>\n

\u3000\u3000\u5bf9 lambda \u51fd\u6570\u547d\u540d\u7684\u552f\u4e00\u4f5c\u7528\u53ef\u80fd\u662f\u51fa\u4e8e\u6559\u5b66\u76ee\u7684\uff0c\u4ee5\u8868\u660e lambda \u51fd\u6570\u7684\u786e\u662f\u548c\u5176\u4ed6\u51fd\u6570\u4e00\u6837\u7684\u51fd\u6570\u2014\u2014\u53ef\u4ee5\u88ab\u8c03\u7528\u5e76\u4e14\u5177\u6709\u67d0\u79cd\u529f\u80fd\u3002\u9664\u6b64\u4e4b\u5916\uff0c\u6211\u4eec\u4e0d\u5e94\u8be5\u5c06 lambda \u51fd\u6570\u8d4b\u503c\u7ed9\u53d8\u91cf\u3002<\/p>\n

\u3000\u3000\u4e3a lambda \u51fd\u6570\u547d\u540d\u7684\u95ee\u9898\u5728\u4e8e\u8fd9\u4f7f\u5f97\u8c03\u8bd5\u4e0d\u90a3\u4e48\u76f4\u89c2\u3002\u4e0e\u5176\u4ed6\u7684\u4f7f\u7528\u5e38\u89c4 def \u5173\u952e\u5b57\u521b\u5efa\u7684\u51fd\u6570\u4e0d\u540c\uff0clambda \u51fd\u6570\u6ca1\u6709\u540d\u5b57\uff0c\u8fd9\u4e5f\u662f\u4e3a\u4ec0\u4e48\u6709\u65f6\u5b83\u4eec\u88ab\u79f0\u4e3a\u533f\u540d\u51fd\u6570\u7684\u539f\u56e0\u3002\u601d\u8003\u4e0b\u9762\u7b80\u5355\u7684\u4f8b\u5b50\uff0c\u627e\u51fa\u7ec6\u5fae\u7684\u533a\u522b\uff1a<\/p>\n

\u3000\u3000>>> inversive0 = lambda x: 1 \/ x<\/p>\n

\u3000\u3000>>> inversive0(2)<\/p>\n

\u3000\u3000 0.5<\/p>\n

\u3000\u3000>>> inversive0(0)<\/p>\n

\u3000\u3000 Traceback (most recent call last):<\/p>\n

File “<input>”, line 1, in <module>
File “<input>”, line 1, in <lambda><\/p>\n

\u3000\u3000 ZeroDivisionError: division by zero<\/p>\n

\u3000\u3000>>> def inversive1(x):<\/p>\n

\u3000\u3000… return 1 \/ x<\/p>\n

\u3000\u3000…<\/p>\n

\u3000\u3000>>> inversive1(2)<\/p>\n

\u3000\u3000 0.5<\/p>\n

\u3000\u3000>>> inversive1(0)<\/p>\n

\u3000\u3000 Traceback (most recent call last):<\/p>\n

File “<input>”, line 1, in <module>
File “<input>”, line 2, in inversive1<\/p>\n

\u3000\u3000 ZeroDivisionError: division by zero<\/p>\n

\u3000\u3000\u5f53\u60a8\u7684\u4ee3\u7801\u5b58\u5728\u5173\u4e8e lambda \u51fd\u6570\u7684\u95ee\u9898(\u5373 inversive0)\uff0cTraceback \u9519\u8bef\u4fe1\u606f\u53ea\u4f1a\u63d0\u793a\u60a8 lambda \u51fd\u6570\u5b58\u5728\u95ee\u9898\u3002<\/p>\n

\u3000\u3000\u76f8\u6bd4\u4e4b\u4e0b\uff0c\u4f7f\u7528\u6b63\u5e38\u5b9a\u4e49\u7684\u51fd\u6570\uff0cTraceback \u4f1a\u6e05\u6670\u5730\u63d0\u793a\u60a8\u6709\u95ee\u9898\u7684\u51fd\u6570(\u5373 inversive1)\u3002<\/p>\n

\u3000\u3000\u4e0e\u6b64\u76f8\u5173\uff0c\u5982\u679c\u60a8\u60f3\u591a\u6b21\u4f7f\u7528 lambda \u51fd\u6570\uff0c\u6700\u4f73\u5b9e\u8df5\u662f\u4f7f\u7528\u901a\u8fc7 def \u5b9a\u4e49\u7684\u5141\u8bb8\u4f7f\u7528\u6587\u6863\u5b57\u7b26\u4e32\u7684\u5e38\u89c4\u51fd\u6570\u3002<\/p>\n

\u3000\u3000 4. \u4e0d\u8981\u5fd8\u8bb0\u5217\u8868\u63a8\u5bfc\u5f0f<\/p>\n

\u3000\u3000\u6709\u4e9b\u4eba\u559c\u6b22\u5c06 lambda \u51fd\u6570\u548c\u9ad8\u9636\u51fd\u6570\u4e00\u8d77\u4f7f\u7528\uff0c\u6bd4\u5982 map \u6216 filter \u3002\u601d\u8003\u4e0b\u9762\u7528\u6cd5\u793a\u4f8b\uff1a<\/p>\n

\u3000\u3000>>> # \u521b\u5efa\u4e00\u4e2a\u6570\u5b57\u5217\u8868<\/p>\n

\u3000\u3000>>> numbers = [2, 1, 3, -3]<\/p>\n

\u3000\u3000>>> # \u4f7f\u7528\u5e26\u6709 lambda \u51fd\u6570\u7684 map \u51fd\u6570<\/p>\n

\u3000\u3000>>> list(map(lambda x: x * x, numbers))<\/p>\n

\u3000\u3000[4, 1, 9, 9]<\/p>\n

\u3000\u3000>>> # \u4f7f\u7528\u5e26\u6709 lambda \u51fd\u6570\u7684 filter \u51fd\u6570<\/p>\n

\u3000\u3000>>> list(filter(lambda x: x % 2, numbers))<\/p>\n

\u3000\u3000[1, 3, -3]<\/p>\n

\u3000\u3000\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u53ef\u8bfb\u6027\u66f4\u5f3a\u7684\u5217\u8868\u63a8\u5bfc\u5f0f\u4ee3\u66ff lambda \u51fd\u6570\u3002\u5982\u4e0b\u6240\u793a\uff0c\u6211\u4eec\u4f7f\u7528\u5217\u8868\u63a8\u5bfc\u5f0f\u6765\u521b\u5efa\u76f8\u540c\u7684\u5217\u8868\u5bf9\u8c61\u3002\u5982\u60a8\u6240\u89c1\uff0c\u4e0e\u5217\u8868\u63a8\u5bfc\u5f0f\u76f8\u6bd4\uff0c\u4e4b\u524d\u5c06 map \u6216 filter \u51fd\u6570\u4e0e lambda \u51fd\u6570\u4e00\u8d77\u4f7f\u7528\u66f4\u9ebb\u70e6\u3002\u56e0\u6b64\uff0c\u5728\u521b\u5efa\u6d89\u53ca\u9ad8\u9636\u51fd\u6570\u7684\u5217\u8868\u65f6\uff0c\u5e94\u8003\u8651\u4f7f\u7528\u5217\u8868\u63a8\u5bfc\u5f0f\u3002<\/p>\n

\u3000\u3000>>> # Use list comprehensions<\/p>\n

\u3000\u3000>>> [x * x for x in numbers]<\/p>\n

\u3000\u3000[4, 1, 9, 9]<\/p>\n

\u3000\u3000>>> [x for x in numbers if x % 2]<\/p>\n

\u3000\u3000[1, 3, -3]<\/p>\n

\u3000\u3000\u7ed3\u8bba<\/p>\n

\u3000\u3000\u5728\u672c\u6587\u4e2d\uff0c\u6211\u4eec\u56de\u987e\u4e86\u4f7f\u7528 lambda \u51fd\u6570\u53ef\u80fd\u4f1a\u72af\u7684\u56db\u4e2a\u5e38\u89c1\u9519\u8bef\u3002\u901a\u8fc7\u907f\u514d\u8fd9\u4e9b\u9519\u8bef\uff0c\u60a8\u5e94\u8be5\u80fd\u5728\u4ee3\u7801\u4e2d\u6b63\u786e\u4f7f\u7528 lambda \u51fd\u6570\u3002<\/p>\n

\u3000\u3000\u4f7f\u7528 lambda \u51fd\u6570\u7684\u7ecf\u9a8c\u51c6\u5219\u662f\u4fdd\u6301\u7b80\u5355\u4ee5\u53ca\u53ea\u5728\u672c\u5730\u4f7f\u7528\u4e00\u6b21\u3002 <\/p><\/div>\n

\u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (0<\/span>) <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n
    \n
  • \n","protected":false},"excerpt":{"rendered":"

    Python \u9ad8\u9636 Lambda …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/207215"}],"collection":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=207215"}],"version-history":[{"count":0,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/207215\/revisions"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=207215"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=207215"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=207215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}