Apache Spark is a fast, open-source operating system. It supports 4 languages: Scala, Java, Python, and R. All of these languages have several pros and cons based on which developers choose their preferred language. Writing code in Scala and Python is comparatively easier than writing in Java. Scala processes and analyses data 10 times faster than that of Python and is more maintainable than Python, a statistically-typed language. Due to these reasons, Scala is the most popularly used programming language for Spark. On the other hand, Python is preferred over Scala in machine learning because it has advanced tools for Data Science and Machine Learning. You should choose a language based on your experience and comfort.