astronomy

Starlark

Starlark is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Starlark rather than just read about it. In short: Starlark is a lightweight, high-level programming language designed for embedded use in applications. It uses a subset of the Python syntax.

Key takeaways

Starlark belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Starlark to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Starlark from memory before moving on to harder problems.

Reference excerpt

Starlark is a lightweight, high-level programming language designed for embedded use in applications. It uses a subset of the Python syntax. By default, the code is deterministic and hermetic.

History Starlark was released in 2015 as part of Bazel under the name Skylark. This first implementation was written in Java. In 2018, the language was renamed Starlark. In 2017, a new implementation of Starlark in Go was announced. In 2021, Meta announced an implementation of Starlark written in Rust, to be used for the Buck build system.

Popularity In addition to the Bazel and Buck build systems, Starlark is used by dozens of projects, including Isopod, skycfg, Uber's Starlark Worker, and Tilt. On GitHub, Starlark is among the top 50 languages based on the developer activity.

Syntax Starlark syntax is a strict subset of Python syntax. Similar to Python syntax, Starlark relies on indentation to delimit blocks, using the off-side rule.

Statements and control flow Starlark's statements include:

The = statement to assign a value to a variable The augmented assignment statements to modify a variable The if statement to execute conditionally a block of code (with else or elif) The for statement to iterate over an iterable object The def statement to define a function The break statement to exit a loop The continue statement to skip the rest of the current iteration and continues with the next The pass statement, serving as a NOP, syntactically needed to create an empty code block The return statement to return a value from a function. The load statement, which replaces Python import, to import a value from another module. Unlike Python, the order of load statements does not affect the semantics of the code. Unlike Python, Starlark statements don't include: while, try, raise, class, with, del, assert, yield, import, match and case.

Freezing To ensure thread safety and support parallel computing, Starlark has a feature called freezing. At the end of the evaluation of a module, all values become immutable. This means that the values that can be accessed from multiple threads can no longer be modified, which removes the risk of race conditions.

References

Worked examples

Example 1 — a first encounter with Starlark

Start with the simplest possible case. Write down what Starlark claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Starlark before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Starlark ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Starlark

In research: Starlark appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Starlark in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Starlark is common in secondary-school and first-year university syllabi. It links to neighbouring topics Programming languages, Programming languages created in 2015, Scripting languages, so understanding it makes those chapters shorter.
In everyday life: Look for Starlark outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Starlark in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Starlark means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Starlark out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Starlark in simple terms?

Starlark is a lightweight, high-level programming language designed for embedded use in applications. It uses a subset of the Python syntax.

Why does Starlark matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Starlark?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Starlark.