Dictionaries are Python implementations of hash tables. They store arbitrary key-value associations, not restricted to a single data type. The dictionaries do not preserve order (no order between elements is defined) so there is no guarantee that any element enumeration will yield a certain order.
This project tries to provide many snippets of Python code that make life easier. Pysheeet website; pysheeet @ GitHub; Issue Tracker; pysheeet as a PDF; Cheat Sheets. C/C cheat sheet; Table of Contents. Get All Keys; Get Key and Value; Find Same Keys; Set a Default Value; Update Dictionary; Merge Two Dictionaries. Dictionaries A dictionary optimizes element lookups. It uses keys and values, instead of numbers as placeholders. Python Cheat Sheet. Common Built in.
NB: unless otherwise specified, everything is Python 2 syntax.
Defining a dictionary:
Initializing a dictionary:
Note: this syntax is also known as dictionary comprehension.
Enumerating all the items in a dictionary:
Looking up an element:
Note: no error is thrown if the element already exists; an overwrite happens.
Using a dictionary as a lookup table to remove duplicates in a list:
Note: a set data type is more suited for such task. There is also a simplified syntax (e.g. list(set(L)) ) that can be used if the element order within the input list does not need to be preserved.
That’s it for today, thank you for your read!
Cheat sheets can be really helpful when you’re trying a set of exercises related to a specific topic, or working on a project. Because you can only fit so much information on a single sheet of paper, most cheat sheets are a simple listing of syntax rules. This set of cheat sheets aims to remind you of syntax rules, but also remind you of important concepts as well. You can click here and download all of the original sheets in a single document.
A more recently updated version of these sheets (April 2021) is available through Leanpub. The updated version includes a sheet that focuses on Git basics, a printer-friendly b&w version of each sheet, and each sheet as a separate document. There is an option to download the fully updated set at no cost.
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- Beginner’s Python Cheat Sheet
- Provides an overview of the basics of Python including variables, lists, dictionaries, functions, classes, and more.
- Beginner’s Python Cheat Sheet - Lists
- Focuses on lists: how to build and modify a list, access elements from a list, and loop through the values in a list. Also covers numerical lists, list comprehensions, tuples, and more.
- Beginner’s Python Cheat Sheet - Dictionaries
- Focuses on dictionaries: how to build and modify a dictionary, access the information in a dictionary, and loop through dictionaries in a variety of ways. Includes sections on nesting lists and dictionaries, using dictionary comprehensions, and more.
- Beginner’s Python Cheat Sheet - If Statements and While Loops
- Focuses on if statements and while loops: how to write conditional tests with strings and numerical data, how to write simple and complex if statements, and how to accept user input. Also covers a variety of approaches to using while loops.
- Beginner’s Python Cheat Sheet - Functions
- Focuses on functions: how to define a function and how to pass information to a function. Covers positional and keyword arguments, return values, passing lists, using modules, and more
- Beginner’s Python Cheat Sheet - Classes
- Focuses on classes: how to define and use a class. Covers attributes and methods, inheritance and importing, and more.
- Beginner’s Python Cheat Sheet - Files and Exceptions
- Focuses on working with files, and using exceptions to handle errors that might arise as your programs run. Covers reading and writing to files, try-except-else blocks, and storing data using the json module.
- Beginner’s Python Cheat Sheet - Testing Your Code
- Focuses on unit tests and test cases. How to test a function, and how to test a class.
Python Dict Time Complexity
- Beginner’s Python Cheat Sheet - Pygame
- Focuses on creating games with Pygame. Creating a game window, rect objects, images, responding to keyboard and mouse input, groups, detecting collisions between game elements, and rendering text
- Beginner’s Python Cheat Sheet - Matplotlib
- Focuses on creating visualizations with Matplotlib. Making line graphs and scatter plots, customizing plots, making multiple plots, and working with time-based data.
- Beginner’s Python Cheat Sheet - Plotly
- Focuses on creating visualizations with Plotly. Making line graphs, scatter plots, and bar graphs, styling plots, making multiple plots, and working with geographical datasets.
- Beginner’s Python Cheat Sheet - Django
- Focuses on creating web apps with Django. Installing Django and starting a project, working with models, building a home page, using templates, using data, and making user accounts.
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Dictionary Python Cheat Sheet For Beginners
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Beginner Python Cheat Sheet