How different are the semantics between Python and JavaScript?

javascript python semantics
Steve picture Steve · Nov 23, 2009 · Viewed 16k times · Source

Both these languages seem extremely similar to me. Although Python supports actual classes instead of being prototype-based, in Python classes are not all that different from functions that generate objects containing values and functions, just as you'd do in JavaScript. On the other hand, JavaScript only supports floating-point numbers and strings as built-in data types.

These seem like fairly shallow differences to me, so these things aside, what are some more important differences between them?

Answer

meder omuraliev picture meder omuraliev · Nov 23, 2009
  1. Classical inheritance in Python, Prototypal inheritance in ECMAScript
  2. ECMAScript is a braces and semicolons language while Python is white-space and indent/block based
  3. No var keyword in Python, implicit globals in ECMAScript, both are lexically scoped
  4. Closures in Python 2.5 and lower ( re: Alex Martelli's comment ) are somewhat "limited" because the bindings are read-only, you can't access private variables like you could in ECMAScript
  5. There's no undefined in Python, exceptions are thrown
  6. Immutable list arrays in Python ( tuples )
  7. No switch statement in Python but instead you're encouraged to use a dictionary in that manner, sometimes its convenient assigning properties to lambdas and executing them
  8. ECMAScript 3 does not have a yield statement, nor let expressions/statements, nor array comprehensions - however these are included in Mozilla's JS which is non-standard
  9. raise vs throw, except vs catch ( Python, JS )
  10. Native Unicode strings in ECMAScript
  11. keyword operators such as and, is, and not are used in Python
  12. Python doesn't support counters such as i++
  13. Python's for loop is "smart" so you don't need to use a counter for enumerating through lists, nor do you run into prototypal properties inherited from Object.prototype
  14. You don't have to use the new operator in Python to create objects
  15. Python is duck-typed

I stole a good bit of info from http://hg.toolness.com/python-for-js-programmers/raw-file/tip/PythonForJsProgrammers.html

Related questions

Django Template Variables and Javascript

When I render a page using the Django template renderer, I can pass in a dictionary variable containing various values to manipulate them in the page using {{ myVar }}. Is there a way to access the same variable in Javascript (perhaps …

Read More
Call Python function from JavaScript code

I'd like to call a Python function from JavaScript code, because there isn't an alternative in JavaScript for doing what I want. Is this possible? Could you adjust the below snippet to work? JavaScript code: var tag = document.getElementsByTagName("p")[0]; …

Read More
Can a website detect when you are using selenium with chromedriver?

I've been testing out Selenium with Chromedriver and I noticed that some pages can detect that you're using Selenium even though there's no automation at all. Even when I'm just browsing manually just using chrome through Selenium and Xephyr I …

Read More