If you pass a mutable object into a method, the method gets a reference to that same object and you can mutate it to your heart's delight, but if you rebind the reference in the method, the outer scope will know nothing about it, and after you're done, the outer reference will still point at the original object.<\/p>\n
If you pass an immutable object to a method, you still can't rebind the outer reference, and you can't even mutate the object.<\/p>\n
\u4f8b\u5982 \u4e0d\u904e\u5982\u679c\u4f60\u628a\u4e00\u500b mutable \u7269\u4ef6\u653e\u9032 immutable \u7269\u4ef6\u88e1\uff0c\u4f8b\u5982\u628a list \u653e\u9032 tuple \u88e1\uff0c\u5247\u4fee\u6539\u4e86 list \u4e4b\u5f8c\uff0c\u90a3\u500b tuple \u88e1\u7684 list \u4e5f\u662f\u6703\u88ab\u4fee\u6539\u3002<\/p>\n Assignment is the binding of a name to an object: \u6240\u8b02\u7684 assign \u9019\u500b\u52d5\u4f5c\uff0c\u5176\u5be6\u662f\u5e6b 'Mollie' \u9019\u500b\u5b57\u4e32\u53d6\u4e00\u500b\u540d\u5b57\u53eb\u505a name\uff0c\u6240\u4ee5\u5982\u679c\u4f60\u53c8\u52a0\u4e0a\u4e00\u53e5 ref: \u53ea\u6709 module\u3001class\u3001function \u624d\u6709\u5efa\u7acb\u65b0\u7684 scope\uff0cif\u3001while\u3001for \u4e26\u4e0d\u6703\u5efa\u7acb\u65b0\u7684 scope\u3002<\/p>\n If you pass a mutable object into a method, the method gets a reference to that same object and you can mutate it to your heart's delight, but if you rebind the reference in the method, the outer scope will know nothing about it, and after you're done, the outer reference will still point at the original object.<\/p>\n If you pass an immutable object to a method, you still can't rebind the outer reference, and you can't even mutate the object.<\/p>\n","protected":false},"author":1,"featured_media":761,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[2],"class_list":["post-244","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-about-python","tag-python"],"_links":{"self":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/posts\/244","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/comments?post=244"}],"version-history":[{"count":0,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/posts\/244\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/media\/761"}],"wp:attachment":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/media?parent=244"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/categories?post=244"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/tags?post=244"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}def foo(bar):<\/code> \u9019\u500b function \u7684\u53c3\u6578\u50b3\u905e\uff0c\u5176\u5be6\u662f\u5728 foo<\/code> \u7684 local namespace \u88e1\u5e6b\u50b3\u9032\u53bb\u7684\u7269\u4ef6\u7d81\u5b9a\u4e86\u4e00\u500b\u53eb\u505a bar<\/code> \u7684\u540d\u5b57\uff08\u6240\u8b02\u7684 assignment\uff09\uff1b\u5982\u679c\u4f60\u5728 foo<\/code> \u88e1 re-assign \u4e86\u4e00\u500b\u65b0\u7684\u7269\u4ef6\u7d66 bar<\/code>\uff0c\u5be6\u969b\u4e0a\u662f\u628a bar<\/code> \u9019\u500b\u540d\u5b57\u7d81\u5b9a\u5230\u90a3\u500b\u65b0\u7684\u7269\u4ef6\u3002<\/p>\n\n
a_list = [1, 2, 3]\na_tuple = (a_list, 'a', 'b', 'c')\na_list.append(4)<\/code><\/pre>\nname = 'Molly'<\/code>.
\nAssignment between names doesn't create a new object, both names are simply bound to the same object: nickname = name<\/code>.<\/p>\nname = 'Mollie'\nname = 'Vinta'<\/code><\/pre>\nname = 'Vinta'<\/code>\uff0c\u5be6\u969b\u4e0a\u662f\u5efa\u7acb\u4e86\u4e00\u500b\u65b0\u7684\u7269\u4ef6\uff08\u5b57\u4e32 'Vinta'\uff09\uff0c\u518d\u628a\u9019\u500b\u65b0\u5b57\u4e32\u7d81\u5b9a\u5230 name \u9019\u500b\u540d\u5b57\u3002<\/p>\n# if bar refers to a mutable object\ndef foo(bar):\n bar.append('new value')\n print(bar)\n # output: ['old value', 'new value']\n\nanswer_list = ['old value', ]\nfoo(answer_list)\nprint(answer_list)\n# output: ['old value', 'new value']\n\n# if bar refers to an immutable object\ndef foo(bar):\n bar = 'new value'\n print(bar)\n # output: 'new value'\n\nanswer_list = 'old value'\nfoo(answer_list)\nprint(answer_list)\n# output: 'old value'\n\n# if bar refers to a mutable object and re-assign it in foo\ndef foo(bar):\n bar = ['new value', ]\n print(bar)\n # output: ['new value', ]\n\nanswer_list = ['old value', ]\nfoo(answer_list)\nprint(answer_list)\n# output: ['old value', ]<\/code><\/pre>\n
\nhttps:\/\/stackoverflow.com\/questions\/986006\/how-do-i-pass-a-variable-by-reference<\/a>
\nhttps:\/\/jeffknupp.com\/blog\/2012\/11\/13\/is-python-callbyvalue-or-callbyreference-neither\/<\/a>
\nhttps:\/\/docs.python.org\/3\/faq\/programming.html#how-do-i-write-a-function-with-output-parameters-call-by-reference<\/a><\/p>\nscope<\/h2>\n
some_list = [\n {\n 'id': 1,\n 'is_change': False,\n },\n {\n 'id': 2,\n 'is_change': False,\n },\n {\n 'id': 3,\n 'is_change': False,\n },\n {\n 'id': 4,\n 'is_change': False,\n },\n]\n\nfor item in some_list:\n item['is_change'] = True<\/code><\/pre>\nsome_list<\/code> \u7684\u6bcf\u500b item \u90fd\u6703\u88ab\u66f4\u65b0\uff0c\u56e0\u70ba\u662f mutable objects \u7684\u884c\u70ba\u662f call-by-reference\u3002\u6240\u4ee5\u4f60\u4e0d\u9700\u8981\u9019\u6a23\uff1a<\/p>\nnew_list = []\nfor item in some_list:\n item['is_change'] = True\n new_list.append(item)<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"