{"id":11780,"date":"2022-09-28T13:46:55","date_gmt":"2022-09-28T08:16:55","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-python-2-7-clean-syntax-for-lvalue-modification\/"},"modified":"2022-09-28T13:46:55","modified_gmt":"2022-09-28T08:16:55","slug":"solved-python-2-7-clean-syntax-for-lvalue-modification","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-python-2-7-clean-syntax-for-lvalue-modification\/","title":{"rendered":"[Solved] Python 2.7 &#8211; clean syntax for lvalue modification"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-45791113\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"45791113\" data-parentid=\"45788271\" data-score=\"0\" data-position-on-page=\"2\" data-highest-scored=\"0\" data-question-has-accepted-highest-score=\"0\" itemprop=\"suggestedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>I feel like we&#8217;ve given the search for pre-existing solutions its due diligence. Given that &#8220;&lt;=&#8221; is assignment in some languages (e.g., Verilog) we can quite intuitively introduce:<\/p>\n<pre><code>value_struct_instance&lt;&lt;='field', value\n<\/code><\/pre>\n<p>as the Pythonic form of<\/p>\n<pre><code>value_struct_instance.field = value\n<\/code><\/pre>\n<p>Here is an updated example for instructive purposes:<\/p>\n<pre><code># Python doesn't support copy-on-assignment, so we must use an\n# immutable object to avoid unintended changes by distant copyholders.\n# As a consequence, the lvalue must be changed on a field update.\n#\n# Currently the only known syntax for updating a field on such an\n# object is:\n#\n#      value_struct_instance&lt;&lt;='field', value\n# \n# https:\/\/stackoverflow.com\/questions\/45788271\/\n\nclass Point(object):\n\n    def __init__(self, x, y, others=None):\n        object.__setattr__(self, 'x', x)\n        object.__setattr__(self, 'y', y)\n\n    def __setattr__(self, name, value):\n        raise AttributeError, \\\n            \"Use \\\"point&lt;&lt;='%s', ...\\\" instead of \\\"point.%s = ...\\\"\" \\\n            % (name, name)\n\n    def __repr__(self):\n        return \"(%d %d)\" % (self.x, self.y)\n\n    def copy(self, x=None, y=None):\n        if x == None: x = self.x\n        if y == None: y = self.y\n        return Point(x, y)\n\n    def __ilshift__(a,b):\n        if   b[0] == 'x': return a.copy(x=b[1])\n        elif b[0] == 'y': return a.copy(y=b[1])\n        else:             raise AttributeError,  \\\n                \"Point has no member '%s'\" % b[0]\n\n    def __eq__ (a,b): return a.x == b.x and a.y == b.y\n    def __ne__ (a,b): return a.x != b.x or  a.y != b.y\n    def __add__(a,b): return Point(a.x+b.x, a.y+b.y)\n    def __sub__(a,b): return Point(a.x-b.x, a.y-b.y)\n\n\n\nmy_very_long_and_complicated_lvalue_expression = [Point(10,10)] * 3\n\n# modify element 0 via \"+=\"\nmy_very_long_and_complicated_lvalue_expression[0] += Point(1,-1)\n\n# modify element 1 via \"&lt;&lt;='field',\" (NEW IDIOM)\nmy_very_long_and_complicated_lvalue_expression[1]&lt;&lt;='x', 15\nprint my_very_long_and_complicated_lvalue_expression\n# result:\n# [(11 9), (15 10), (10 10)]\n\nmy_very_long_and_complicated_lvalue_expression[1]&lt;&lt;='y', 25\nprint my_very_long_and_complicated_lvalue_expression\n# result:\n# [(11 9), (15 25), (10 10)]\n\n# Attempt to modify element 2 via \".field=\"\nmy_very_long_and_complicated_lvalue_expression[2].y = 25\n# result:\n# AttributeError: Use \"point&lt;&lt;='y', ...\" instead of \"point.y = ...\"\n<\/code><\/pre>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">4<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved Python 2.7 &#8211; clean syntax for lvalue modification <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] I feel like we&#8217;ve given the search for pre-existing solutions its due diligence. Given that &#8220;&lt;=&#8221; is assignment in some languages (e.g., Verilog) we can quite intuitively introduce: value_struct_instance&lt;&lt;=&#8217;field&#8217;, value as the Pythonic form of value_struct_instance.field = value Here is an updated example for instructive purposes: # Python doesn&#8217;t support copy-on-assignment, so we must &#8230; <a title=\"[Solved] Python 2.7 &#8211; clean syntax for lvalue modification\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-python-2-7-clean-syntax-for-lvalue-modification\/\" aria-label=\"More on [Solved] Python 2.7 &#8211; clean syntax for lvalue modification\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[3221,3220,349,499,458],"class_list":["post-11780","post","type-post","status-publish","format-standard","hentry","category-solved","tag-lvalue","tag-mutable","tag-python","tag-python-2-7","tag-struct"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] Python 2.7 - clean syntax for lvalue modification - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-python-2-7-clean-syntax-for-lvalue-modification\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Python 2.7 - clean syntax for lvalue modification - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] I feel like we&#8217;ve given the search for pre-existing solutions its due diligence. Given that &#8220;&lt;=&#8221; is assignment in some languages (e.g., Verilog) we can quite intuitively introduce: value_struct_instance&lt;&lt;=&#039;field&#039;, value as the Pythonic form of value_struct_instance.field = value Here is an updated example for instructive purposes: # Python doesn&#039;t support copy-on-assignment, so we must ... 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Given that &#8220;&lt;=&#8221; is assignment in some languages (e.g., Verilog) we can quite intuitively introduce: value_struct_instance&lt;&lt;='field', value as the Pythonic form of value_struct_instance.field = value Here is an updated example for instructive purposes: # Python doesn't support copy-on-assignment, so we must ... 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