diff --git a/sources/tech/20210309 Learn Python dictionary values with Jupyter.md b/sources/tech/20210309 Learn Python dictionary values with Jupyter.md deleted file mode 100644 index a54b7f58a8..0000000000 --- a/sources/tech/20210309 Learn Python dictionary values with Jupyter.md +++ /dev/null @@ -1,167 +0,0 @@ -[#]: subject: (Learn Python dictionary values with Jupyter) -[#]: via: (https://opensource.com/article/21/3/dictionary-values-python) -[#]: author: (Lauren Maffeo https://opensource.com/users/lmaffeo) -[#]: collector: (lujun9972) -[#]: translator: (DCOLIVERSUN) -[#]: reviewer: ( ) -[#]: publisher: ( ) -[#]: url: ( ) - -Learn Python dictionary values with Jupyter -====== -Implementing data structures with dictionaries helps you access -information more quickly. -![Hands on a keyboard with a Python book ][1] - -Dictionaries are the Python programming language's way of implementing data structures. A Python dictionary consists of several key-value pairs; each pair maps the key to its associated value. - -For example, say you're a teacher who wants to match students' names to their grades. You could use a Python dictionary to map the keys (names) to their associated values (grades). - -If you need to find a specific student's grade on an exam, you can access it from your dictionary. This lookup shortcut should save you time over parsing an entire list to find the student's grade. - -This article shows you how to access dictionary values through each value's key. Before you begin the tutorial, make sure you have the [Anaconda package manager][2] and [Jupyter Notebook][3] installed on your machine. - -### 1\. Open a new notebook in Jupyter - -Begin by opening Jupyter and running it in a tab in your web browser. Then: - - 1. Go to **File** in the top-left corner. - 2. Select **New Notebook**, then **Python 3**. - - - -![Create Jupyter notebook][4] - -(Lauren Maffeo, [CC BY-SA 4.0][5]) - -Your new notebook starts off untitled, but you can rename it anything you'd like. I named mine **OpenSource.com Data Dictionary Tutorial**. - -The line number you see in your new Jupyter notebook is where you will write your code. (That is, your input.) - -On macOS, you'll hit **Shift** then **Return** to receive your output. Make sure to do this before creating new line numbers; otherwise, any additional code you write might not run. - -### 2\. Create a key-value pair - -Write the keys and values you wish to access in your dictionary. To start, you'll need to define what they are in the context of your dictionary: - - -``` -empty_dictionary = {} -grades = { -    "Kelsey": 87, -    "Finley": 92 -} - -one_line = {a: 1, b: 2} -``` - -![Code for defining key-value pairs in the dictionary][6] - -(Lauren Maffeo, [CC BY-SA 4.0][5]) - -This allows the dictionary to associate specific keys with their respective values. Dictionaries store data by name, which allows faster lookup. - -### 3\. Access a dictionary value by its key - -Say you want to find a specific dictionary value; in this case, a specific student's grade. To start, hit **Insert** then **Insert Cell Below**. - -![Inserting a new cell in Jupyter][7] - -(Lauren Maffeo, [CC BY-SA 4.0][5]) - -In your new cell, define the keys and values in your dictionary. - -Then, find the value you need by telling your dictionary to print that value's key. For example, look for a specific student's name—Kelsey: - - -``` -# Access data in a dictionary -grades = { -    "Kelsey": 87, -    "Finley": 92 -} - -print(grades["Kelsey"]) -87 -``` - -![Code to look for a specific value][8] - -(Lauren Maffeo, [CC BY-SA 4.0][5]) - -Once you've asked for Kelsey's grade (that is, the value you're trying to find), hit **Shift** (if you're on macOS), then **Return**. - -You see your desired value—Kelsey's grade—as an output below your cell. - -### 4\. Update an existing key - -What if you realize you added the wrong grade for a student to your dictionary? You can fix it by updating your dictionary to store an additional value. - -To start, choose which key you want to update. In this case, say you entered Finley's grade incorrectly. That is the key you'll update in this example. - -To update Finley's grade, insert a new cell below, then create a new key-value pair. Tell your cell to print the dictionary, then hit **Shift** and **Return**: - - -``` -grades["Finley"] = 90 -print(grades) - -{'Kelsey': 87; "Finley": 90} -``` - -![Code for updating a key][9] - -(Lauren Maffeo, [CC BY-SA 4.0][5]) - -The updated dictionary, with Finley's new grade, appears as your output. - -### 5\. Add a new key - -Say you get a new student's grade for an exam. You can add that student's name and grade to your dictionary by adding a new key-value pair. - -Insert a new cell below, then add the new student's name and grade as a key-value pair. Once you're done, tell your cell to print the dictionary, then hit **Shift** and **Return**: - - -``` -grades["Alex"] = 88 -print(grades) - -{'Kelsey': 87, 'Finley': 90, 'Alex': 88} -``` - -![Add a new key][10] - -(Lauren Maffeo, [CC BY-SA 4.0][5]) - -All key-value pairs should appear as output. - -### Using dictionaries - -Remember that keys and values can be any data type, but it's rare for them to be [non-primitive types][11]. Additionally, dictionaries don't store or structure their content in any specific order. If you need an ordered sequence of items, it's best to create a list in Python, not a dictionary. - -If you're thinking of using a dictionary, first confirm if your data is structured the right way, i.e., like a phone book. If not, then using a list, tuple, tree, or other data structure might be the best option. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/21/3/dictionary-values-python - -作者：[Lauren Maffeo][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/lmaffeo -[b]: https://github.com/lujun9972 -[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/python-programming-code-keyboard.png?itok=fxiSpmnd (Hands on a keyboard with a Python book ) -[2]: https://docs.anaconda.com/anaconda/ -[3]: https://opensource.com/article/18/3/getting-started-jupyter-notebooks -[4]: https://opensource.com/sites/default/files/uploads/new-jupyter-notebook.png (Create Jupyter notebook) -[5]: https://creativecommons.org/licenses/by-sa/4.0/ -[6]: https://opensource.com/sites/default/files/uploads/define-keys-values.png (Code for defining key-value pairs in the dictionary) -[7]: https://opensource.com/sites/default/files/uploads/jupyter_insertcell.png (Inserting a new cell in Jupyter) -[8]: https://opensource.com/sites/default/files/uploads/lookforvalue.png (Code to look for a specific value) -[9]: https://opensource.com/sites/default/files/uploads/jupyter_updatekey.png (Code for updating a key) -[10]: https://opensource.com/sites/default/files/uploads/jupyter_addnewkey.png (Add a new key) -[11]: https://www.datacamp.com/community/tutorials/data-structures-python diff --git a/translated/tech/20210309 Learn Python dictionary values with Jupyter.md b/translated/tech/20210309 Learn Python dictionary values with Jupyter.md new file mode 100644 index 0000000000..2b50efa1f2 --- /dev/null +++ b/translated/tech/20210309 Learn Python dictionary values with Jupyter.md @@ -0,0 +1,166 @@ +[#]: subject: (Learn Python dictionary values with Jupyter) +[#]: via: (https://opensource.com/article/21/3/dictionary-values-python) +[#]: author: (Lauren Maffeo https://opensource.com/users/lmaffeo) +[#]: collector: (lujun9972) +[#]: translator: (DCOLIVERSUN) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) + +用 Jupyter 学习 Python 字典 +====== +字典数据结构可以帮助你快速访问信息。 +![Python书与放在键盘上的手 ][1] + +字典是 Python 编程语言使用的数据结构。一个 Python 字典由多个键值对组成；每个对将键映射到其关联的值上。 + +例如你是一名老师，想把学生姓名与成绩对应起来。你可以使用 Python 字典，将学生姓名映射到他们关联的成绩上。此时，键值对中键是姓名，值是对应的成绩。 + +如果你想知道某个学生的考试成绩，你可以从字典中访问。这种快捷查询方式可以为你节省解析整个列表找到学生成绩的时间。 + +本文介绍了如何通过键访问对应的字典值。学习前，请确保你已经安装了[Anaconda 包管理器][2]和 [Jupyter 笔记本][3]。 + +### 1\. 在 Jupyter 中打开一个新的笔记本 + +首先打开并在 Web 浏览器中运行 Jupyter。然后， + + 1. 转到左上角的 **文件**。 + 2. 选择 **新笔记本**，点击 **Python 3**。 + + + +![新建 Jupyter 笔记本][4] + +(Lauren Maffeo, [CC BY-SA 4.0][5]) + +开始时，新建的笔记本是无标题的，你可以将其重命名为任何名称。我为我的笔记本取名为 **OpenSource.com 数据字典教程**。 + +笔记本中标有行号的位置就是你写代码的区域，也是你输入的位置。 + +在 macOS 上，可以同时按 **Shift**、 **Return**键得到输出。在创建新的代码区域前，请确保完成上述行为；否则，你写的任何附加代码可能无法运行。 + +### 2\. 新建一个键值对 + +在字典中输入你希望访问的键与值。输入前，你需要在字典上下文中定义它们的含义： + + +``` +empty_dictionary = {} +grades = { +    "Kelsey": 87, +    "Finley": 92 +} + +one_line = {a: 1, b: 2} +``` + +![定义字典键值对的代码][6] + +(Lauren Maffeo, [CC BY-SA 4.0][5]) + +这段代码让字典将特定键与其各自的值关联起来。字典按名称存储数据，从而可以更快地查询。 + +### 3\. 通过键访问字典值 + +现在你想查询指定的字典值；在上述例子中，字典值指特定学生的成绩。首先，点击 **Insert** 后选择 **Insert Cell Below**。 + +![在 Jupyter 插入新建单元格][7] + +(Lauren Maffeo, [CC BY-SA 4.0][5]) + +在新单元格中，定义字典中的键与值。 + +然后，告诉字典打印该值的键，找到需要的值。例如，查询名为 Kelsey 的学生的成绩： + + +``` +# 访问字典中的数据 +grades = { +    "Kelsey": 87, +    "Finley": 92 +} + +print(grades["Kelsey"]) +87 +``` + +![查询特定值的代码][8] + +(Lauren Maffeo, [CC BY-SA 4.0][5]) + +当你查询 Kelsey 的成绩（也就是你想要查询的值）时，如果你用的是 macOS，只需要同时按 **Shift**、 **Return** 键。 + +你会在单元格下方看到 Kelsey 的成绩。 + +### 4\. 更新已有的键 + +当把一位学生的错误成绩添加到字典时，你会怎么办？可以通过更新字典、存储新值来修正这类错误。 + +首先，选择你想更新的那个键。在上述例子中，假设你错误地输入了 Finley 的成绩，那么 Finley 就是你需要更新的键。 + +为了更新 Finley 的成绩，你需要在下方插入新的单元格，然后创建一个新的键值对。同时按 **Shift**、 **Return** 键打印字典全部信息： + + +``` +grades["Finley"] = 90 +print(grades) + +{'Kelsey': 87; "Finley": 90} +``` + +![更新键的代码][9] + +(Lauren Maffeo, [CC BY-SA 4.0][5]) + +单元格下方输出带有 Finley 更新成绩的字典。 + +### 5\. 添加新键 + +假设你得到一位新学生的考试成绩。你可以用新键值对将那名学生的姓名与成绩补充到字典中。 + +插入新的单元格，以键值对形式添加新学生的姓名与成绩。当你完成这些后，同时按 **Shift**、 **Return** 键打印字典全部信息： + + +``` +grades["Alex"] = 88 +print(grades) + +{'Kelsey': 87, 'Finley': 90, 'Alex': 88} +``` + +![添加新键][10] + +(Lauren Maffeo, [CC BY-SA 4.0][5]) + +所有的键值对输出在单元格下方。 + +### 使用字典 + +请记住，键与值可以是任意数据类型，但它们很少是[扩展数据类型non-primitive types>>][11]。此外，字典不能以指定的顺序存储、组织里面的数据。如果你想要数据有序，最好使用 Python 列表，而非字典。 + +如果你考虑使用字典，首先要确认你的数据结构是否是合适的，例如像电话簿的结构。如果不是，列表、元组、树或者其他数据结构可能是更好的选择。 + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/21/3/dictionary-values-python + +作者：[Lauren Maffeo][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/lmaffeo +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/python-programming-code-keyboard.png?itok=fxiSpmnd (Hands on a keyboard with a Python book ) +[2]: https://docs.anaconda.com/anaconda/ +[3]: https://opensource.com/article/18/3/getting-started-jupyter-notebooks +[4]: https://opensource.com/sites/default/files/uploads/new-jupyter-notebook.png (Create Jupyter notebook) +[5]: https://creativecommons.org/licenses/by-sa/4.0/ +[6]: https://opensource.com/sites/default/files/uploads/define-keys-values.png (Code for defining key-value pairs in the dictionary) +[7]: https://opensource.com/sites/default/files/uploads/jupyter_insertcell.png (Inserting a new cell in Jupyter) +[8]: https://opensource.com/sites/default/files/uploads/lookforvalue.png (Code to look for a specific value) +[9]: https://opensource.com/sites/default/files/uploads/jupyter_updatekey.png (Code for updating a key) +[10]: https://opensource.com/sites/default/files/uploads/jupyter_addnewkey.png (Add a new key) +[11]: https://www.datacamp.com/community/tutorials/data-structures-python