为什么 PyScripter 控制台中的输出不同？

Question

从 PyScripter (3.6.4.0) REPL 控制台：

*** Python 3.7.7 (tags/v3.7.7:d7c567b08f, Mar 10 2020, 10:41:24) [MSC v.1900 64 bit (AMD64)] on win32. ***
*** Remote Python engine is active ***
>>> d = {}
>>> d['B'] = 12
>>> d['A'] = 10
>>> d['C'] = 34
>>> d
{'A': 10, 'B': 12, 'C': 34}

这个结果让我们相信 Python 对键进行排序并且不保留插入顺序，而从 3.6 版本开始就可以保证。

现在让我们在 PyScripter 之外的控制台中运行完全相同版本的 Python：

Python 3.7.7 (tags/v3.7.7:d7c567b08f, Mar 10 2020, 10:41:24) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> d = {}
>>> d['B'] = 12
>>> d['A'] = 10
>>> d['C'] = 34
>>> d
{'B': 12, 'A': 10, 'C': 34}

插入顺序保存好。

为什么输出不同？

Answer 1

在 pyscripter REPL 中，当我不依赖 REPL 提供答案而是使用print语句时，我得到了正确的结果：

>>> print(d)
{'B': 12, 'A': 10, 'C': 34}

where 只d产生键，就好像它们被排序一样：

>>> d
{'A': 10, 'B': 12, 'C': 34}

因此，当涉及到字典顺序时，不要相信 pyscripter REPL 输出。

Answer 2

您需要在 pyscripter 中禁用Pretty print 输出选项：

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如果选中，则标准 python 模块 pprint 用于格式化解释器输出。

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在选项 > IDE 选项 > Python 解释器下找到它。

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该pprint模块按排序的键顺序输出字典，忽略字典的当前顺序。从文档中：

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在计算显示之前，字典按键排序。

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It\xe2\x80\x99s 不是匹配旧 Python 版本输出的 hack，因为在 Python 3.6 之前，顺序取决于插入和删除顺序加上随机哈希种子。

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相反，使用pprint当输出变得笨拙时，通过使用换行符和缩进，使用可以提供更好的输出，其中标准表示将所有内容放在一行上。

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你的具体例子并没有真正体现出差异，更长的字典会让它更清楚：

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>>> from requests import get\n>>> from secrets import token_hex\n>>> from pprint import pprint\n>>> fortunes = {token_hex(4): get("https://fortuneapi.herokuapp.com/").text for _ in range(5)}\n>>> print(repr(fortunes))  # standard REPL output prints the repr() result\n{\'a33435f0\': \'"If reporters don\\\'t know that truth is plural, they ought to be lawyers.\\\\n\\\\t\\\\t-- Tom Wicker\\\\n"\\n\', \'1f08db3c\': \'"Very few profundities can be expressed in less than 80 characters.\\\\n"\\n\', \'6037e01e\': \'"The main problem I have with cats is, they\\\'re not dogs.\\\\n\\\\t\\\\t-- Kevin Cowherd\\\\n"\\n\', \'b817eaf8\': \'"New York now leads the world\\\'s great cities in the number of people around\\\\nwhom you shouldn\\\'t make a sudden move.\\\\n\\\\t\\\\t-- David Letterman\\\\n"\\n\', \'c89994e7\': \'"I\\\'m GLAD I remembered to XEROX all my UNDERSHIRTS!!\\\\n"\\n\'}\n>>> pprint(fortunes)  # pprint outputs pretty-printed lines, sorted.\n{\'1f08db3c\': \'"Very few profundities can be expressed in less than 80 \'\n             \'characters.\\\\n"\\n\',\n \'6037e01e\': \'"The main problem I have with cats is, they\\\'re not \'\n             \'dogs.\\\\n\\\\t\\\\t-- Kevin Cowherd\\\\n"\\n\',\n \'a33435f0\': \'"If reporters don\\\'t know that truth is plural, they ought to be \'\n             \'lawyers.\\\\n\\\\t\\\\t-- Tom Wicker\\\\n"\\n\',\n \'b817eaf8\': \'"New York now leads the world\\\'s great cities in the number of \'\n             "people around\\\\nwhom you shouldn\'t make a sudden "\n             \'move.\\\\n\\\\t\\\\t-- David Letterman\\\\n"\\n\',\n \'c89994e7\': \'"I\\\'m GLAD I remembered to XEROX all my UNDERSHIRTS!!\\\\n"\\n\'}\n

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如果您只是偶尔需要检查字典的特定项目顺序，您可以启用该选项，然后使用print(dictionary)在特殊情况下使用。

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您还可以将sort_dicts=False参数传递给pprint()，前提是您手动调用它；功能pprint.pp()​甚至将其设为默认值：

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>>> from pprint import pp\n>>> pp(fortunes)\n{\'a33435f0\': \'"If reporters don\\\'t know that truth is plural, they ought to be \'\n             \'lawyers.\\\\n\\\\t\\\\t-- Tom Wicker\\\\n"\\n\',\n \'1f08db3c\': \'"Very few profundities can be expressed in less than 80 \'\n             \'characters.\\\\n"\\n\',\n \'6037e01e\': \'"The main problem I have with cats is, they\\\'re not \'\n             \'dogs.\\\\n\\\\t\\\\t-- Kevin Cowherd\\\\n"\\n\',\n \'b817eaf8\': \'"New York now leads the world\\\'s great cities in the number of \'\n             "people around\\\\nwhom you shouldn\'t make a sudden "\n             \'move.\\\\n\\\\t\\\\t-- David Letterman\\\\n"\\n\',\n \'c89994e7\': \'"I\\\'m GLAD I remembered to XEROX all my UNDERSHIRTS!!\\\\n"\\n\'\n}\n

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或者您可以要求 PyScripter 项目在其控制台实现中使用该选项。

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