Python3基础 list(dict) 使用 * 扩充时，出现字典元素重复问题

 

•        Python : 3.7.3
•          OS : Ubuntu 18.04.2 LTS
•         IDE : pycharm-community-2019.1.3
•       Conda : 4.7.5
•    typesetting : Markdown

 

code

coder@ubuntu:~$ source activate py37
(py37) coder@ubuntu:~$ ipython
Python 3.7.3 (default, Mar 27 2019, 22:11:17)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.5.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: a = [{}] * 3                                                            

In [2]: a
Out[2]: [{}, {}, {}]

In [3]: id(a[0]), id(a[1]), id(a[2])  

Out[3]: (140086817892752, 140086817892752, 140086817892752)

In [4]: a[0]["lang"] = "python"  # 看到这里我明白了，那个乘号扩展的是引用、标记，只有一个dict对象。再做一下测试。                                               

In [5]: a
Out[5]: [{'lang': 'python'}, {'lang': 'python'}, {'lang': 'python'}]

In [6]: exit
(py37) coder@ubuntu:~$ conda deactivate
coder@ubuntu:~$

 

more_knowledge

coder@ubuntu:~$ source activate py37
(py37) coder@ubuntu:~$ ipython
Python 3.7.3 (default, Mar 27 2019, 22:11:17)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.5.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: a = []                                                                  

In [2]: a.append(dict())                                                        

In [3]: a.append(dict())                                                        

In [4]: a
Out[4]: [{}, {}]

In [5]: id(a[0]), id(a[1])
Out[5]: (140174650278320, 140174650281416)

In [6]: # 难道只能按照csdn的u011550708博主所说的"必须要对每个dict单独定义"，还有更好的办法吗？有待学习.                                               

In [7]: # 感谢前辈的经验贴，后生学习了！                                        

In [8]: exit
(py37) coder@ubuntu:~$ conda deactivate
coder@ubuntu:~$ 

 

reference

• https://blog.csdn.net/u011550708/article/details/79917777

 

resource

• [文档 - English] docs.python.org/3
• [文档 - 中文] docs.python.org/zh-cn/3
• [规范] www.python.org/dev/peps/pep-0008
• [规范] zh-google-styleguide.readthedocs.io/en/latest/google-python-styleguide/python_language_rules
• [源码] www.python.org/downloads/source
• [ PEP ] www.python.org/dev/peps
• [平台] www.cnblogs.com
• [平台] gitee.com

 

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Python具有开源、跨平台、解释型、交互式等特性，值得学习。

Python的设计哲学：优雅，明确，简单。提倡用一种方法，最好是只有一种方法来做一件事。

代码的书写要遵守规范，这样有助于沟通和理解。

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