From 6694401bc4fce5ffe0fe05e01bacfdb18b589f58 Mon Sep 17 00:00:00 2001 From: DarkSun Date: Wed, 10 Mar 2021 05:21:12 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98[tech]:=2020210309=20Learn=20?= =?UTF-8?q?Python=20dictionary=20values=20with=20Jupyter?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sources/tech/20210309 Learn Python dictionary values with Jupyter.md --- ...n Python dictionary values with Jupyter.md | 167 ++++++++++++++++++ 1 file changed, 167 insertions(+) create mode 100644 sources/tech/20210309 Learn Python dictionary values with Jupyter.md diff --git a/sources/tech/20210309 Learn Python dictionary values with Jupyter.md b/sources/tech/20210309 Learn Python dictionary values with Jupyter.md new file mode 100644 index 0000000000..3a227897a6 --- /dev/null +++ b/sources/tech/20210309 Learn Python dictionary values with Jupyter.md @@ -0,0 +1,167 @@ +[#]: 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: ( ) +[#]: 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