However, Byterun was designed originally as a learning exercise, so speed is not important to us.
#CONTACT BOOK IN PYTHON SOURCE CODE CODE#
The biggest disadvantage is speed: executing code via Byterun is much slower than executing it in CPython, where the interpreter is written in C and carefully optimized. Writing a Python interpreter in Python has both advantages and disadvantages. (Indeed, the widely used C compiler gcc is written in C.) You could write a Python interpreter in almost any language. This may strike you as odd, but it's no more odd than writing a C compiler in C. A Python Python Interpreterīyterun is a Python interpreter written in Python. As we'll see later in the chapter, the Python compiler has much less information about the behavior of a program than a C compiler does. The reason Python is called "interpreted" is that the compilation step does relatively less work (and the interpreter does relatively more) than in a compiled language. Most interpreted languages, including Python, do involve a compilation step. However, this terminology isn't as precise as it may seem. Python is often called an "interpreted" language like Ruby or Perl, as opposed to a "compiled" language like C or Rust. You may be surprised to hear that compiling is a step in executing Python code at all. The interpreter's job is to take these code objects and follow the instructions. Together, these steps transform the programmer's source code from lines of text into structured code objects containing instructions that the interpreter can understand. In this chapter, "interpreter" has a more narrow meaning: it's the last step in the process of executing a Python program.īefore the interpreter takes over, Python performs three other steps: lexing, parsing, and compiling. Sometimes people use "the Python interpreter" more or less interchangeably with "Python" to talk about executing Python code from start to finish. Sometimes interpreter refers to the Python REPL, the interactive prompt you get by typing python at the command line.
The word "interpreter" can be used in a variety of different ways when discussing Python.
A Python Interpreterīefore we begin, let's narrow down what we mean by "a Python interpreter". (If you don't know which Python you're using, it's probably CPython.) Despite its short length, Byterun is capable of running most simple Python programs 1. Its structure is similar to the primary implementation of Python, CPython, so understanding Byterun will help you understand interpreters in general and the CPython interpreter in particular.
The goal is not to explain everything there is to know about interpreters-like so many interesting areas of programming and computer science, you could devote years to developing a deep understanding of the topic.īyterun was written by Ned Batchelder and myself, building on the work of Paul Swartz. This chapter will walk through the structure of the interpreter and give you enough context to explore it further. Through my work on Byterun, I was surprised and delighted to discover that the fundamental structure of the Python interpreter fits easily into the 500-line size restriction. Introductionīyterun is a Python interpreter implemented in Python. (This chapter is also available in Simplified Chinese). She's spoken at P圜on North America about Python internals and loves weird bugs. Before Dropbox, she was a facilitator at the Recurse Center, a writers retreat for programmers in New York. Allison is an engineer at Dropbox, where she helps maintain one of the largest networks of Python clients in the world.
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