Cheat sheets for Python: 
Python is a popular choice for beginners, yet still powerful enough to back some of the world’s most popular products and applications. It’s design makes the programming experience feel almost as natural as writing in English. Python basics or Python Debugger cheatsheets for beginners covers important syntax to get started. Community-provided libraries such as numpy, scipy, sci-kit and pandas are highly relied on and the NumPy/SciPy/Pandas Cheat Sheet provides a quick refresher to these. 
Python 2.7 Quick Reference SheetPython Cheat Sheet by DaveChildPython Basics Reference sheetPython Debugger CheatsheetNumPy / SciPy / Pandas Cheat SheetPython OverAPI cheatsheetPython Decorators cheatsheetPython 2.4 Quick Reference CardPython 3 Cheat SheetPython Language & Syntax Cheat Sheet

Cheat sheets for R: 
The R’s ecosystem has been expanding so much that a lot of referencing is needed. The R Reference Card covers most of the R world in few pages.The Rstudio has also published a series of cheatsheets to make it easier for the R community. The data visualization with ggplot2 seems to be a favorite as it helps when you are working on creating graphs of your results. 
R cheat sheet (Google Drive)R functions for Regression AnalysisR Reference CardR functions for Time series AnalysisR Reference Card for Data MiningR Cheat SheetData Analysis the data.table wayInteractive Web Apps cheatsheet by R studioData Visualisation with ggplot2 cheatsheet by R studioPackage Development with devtools cheatsheet by R studioData Wrangling cheatsheetR markdown cheatsheetR Markdown Reference guideR Data Management cheatsheetR Cheatsheet for graphical parameters

Cheat sheets for MySQL & SQL: 
For a data scientist basics of SQL are as important as any other language as well. Both PIG and Hive Query Language are closely associated with SQL- the original Structured Query Language. SQL cheatsheets provide a 5 minute quick guide to learning it and then you may explore Hive & MySQL! MySQL Cheatsheet by Dave childSQL Cheat sheetSQL in one pageMySQL Reference guideVisual SQL JoinsSQL for dummies

Cheat sheets for Spark: 
Apache Spark is an engine for large-scale data processing. For certain applications, such as iterative machine learning, Spark can be up to 100x faster than Hadoop (using MapReduce). The essentials of Apache Spark cheatsheet explains its place in the big data ecosystem, walks through setup and creation of a basic Spark application, and explains commonly used actions and operations.
https://dzone.com/refcardz/apache-sparkScala cheatsheets 1Scala cheatsheets 2Scala from DZone Reference CardSpark cheatsheet on githubScala on Spark CheatsheetEssential Apache Spark cheatsheet by MapR

Cheat sheets for Hadoop & Hive: 
Hadoop emerged as an untraditional tool to solve what was thought to be unsolvable by providing an open source software framework for the parallel processing of massive amounts of data. Explore the Hadoop cheatsheets to find out Useful commands when using Hadoop on the command line. A combination of SQL & Hive functions is another one to check out. Hadoop for Dummies cheatsheetGetting Started Apache Hadoop Reference CardHadoop Command Line cheatsheetWorking with HDFS from the command line – Hadoop Cheat sheetHive Function cheatsheetSQL to Hive cheatsheet

Cheat sheets for Machine learning: 
We often find ourselves spending time thinking which algorithm is best? And then go back to our big books for reference! These cheat sheets gives an idea about both the nature of your data and the problem you’re working to address, and then suggests an algorithm for you to try. Choosing the right estimator Machine Learning cheatsheetPatterns for Predictive learning cheatsheetMachine learning algorithm cheat sheet for Microsoft AzureMachine Learning cheatsheet Github 1Machine Learning cheatsheet Github 2Machine Learning which algorithm performs best?Cheat sheet 10 machine learning algorithms R commandsPatterns for Predictive Analytics

Cheat sheets for Django : 
Django is a free and open source web application framework, written in Python. If you are new to Django, you can go over these cheatsheets and brainstorm quick concepts and dive in each one to a deeper level. Django cheat sheet v.1Django cheatsheet 1Django cheatsheet 2Django cheatsheet 3Django cheatsheet 4Django Reference CheatsheetDjango Quick start guide & CheatsheetFlask Cheatsheet

Originally posted by Bhavya Geethika